PyCon 2010

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PyCon 2010TutorialsIntroduction to TraitsA Long Pinax TutorialHacking the Social WebDjango Deployment WorkshopKeynote: Building the Python CommunityKeynote: GvRRealtime webVisTrailsPackaging and Dependencies And StuffDatabase ScalabilityMaximize your program's LazinessRing of PythonPython PatternsNon-standard use of DjangoFriday Evening Lightening TalksWhat an Open Space Lawyer actually doesThe Next Big Programming BookDon't Write Big ApplicationsWhat's new in coverage.pyPython DocxActiveStateProgress DatabaseBetter ways to debug the Cpython runtimeVoice recognition with PythonUbuntu oneSaturday Morning Lightening Talkshaystack django searchtwisted needs youpython translation partyPycon by the numbersState of Ironport KeynoteState PyPyMark Shuttleworth Keynote: Things Open S ...ASync IO DemystifiedCooperative Multitasking with TwistedInterfaces, Adapters, and FactoriesMastering Team Play: 4 examples of compo ...Actors: What, Why, and HowTools for Python MetaprogrammingPython's Dusty Cornerspony-buildSeatle: Open P2P ComputingSaturday Afternoon Lightening talksGvR Python Community service awardKen WhitesellScrape Python Debugging TechniquesGeo Tagging in Python / PhatchBig Brothers Design RulesPyCon SwagPython in tiny embedded systemsPyCharmPEP 385: hg conversionPython - Hell YeahOpen SpacesTesting in Python BoFapp-engineSunday Morning Lightening talksdamn... overslept and missed morning lig ...molly m.ox.ac.ukEventletModern version control: mercurial intern ...New *and* Improved UnittestSaturday afternoon lightening talkMichael Foord ramblingsReal harm of functional programmingBSD and pythonPlease PirateSelf Publishing a Tech BookCeleryVim and PDBFork() vs ThreadsThe most biggest gamest in the worldestOrbinsonPython community in IndiaEuroSciPy 2010Sprintstools to check outsites to check outtalks to try to be sure to watch on vidGood quotesthings to do when I get backkey to iconsExcellent talkNice / Good talkScary/Dangerous (in a good way)Thought provokingDisappointing talkHappy to see thisTODO / Learn thisMore talks in folder
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PyCon 2010
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Tutorials
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Introduction to Traits
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Traits
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Corran Webster
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Enthought
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mathematician
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working in python since 95
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Enthought tool suite
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Traits
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foundation layer on bottom of each of:
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traitsUI
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traits + wx/QT
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kiva
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display pdf
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2-D
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enable
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interactive drawing
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chaco
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2-d interactive plots
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zoom
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live data updates
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mayavi
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3d visualization of scientific data based on vtk
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probably most mature
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envisage
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traits
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provides python attributes
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for
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visualization
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notification
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standardization
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initialization
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validation
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delegation
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from enthought.traits.api import HasTraits, Float
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class Rectangle(HasTraits):
width = Float
height = Float
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types
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Basic types
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Bool
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Complex
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Float
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Int
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Long
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Str
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List
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Dict
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Tuple
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Set
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Instance
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Array
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a numpy numpy.ndarray
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Date
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datetime
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Time
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each of these has a casting version as well
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CFloat
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casting version of Float
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will call float() on whatever is being sent as an assignment
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types for functions, methods, classes, modules, types, weak references, but these are less frequently used
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other useful types
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Any
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any value
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Enum
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One of a set of values
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Range
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String
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a validated string
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string length
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or matches a regex
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Constant
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Event
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write only, no value
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HTML
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HTML text
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Code
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Python code string
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File
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a filename
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Directory
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aa directory name
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UUID
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random UUID
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List Traits
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a = List
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same as List(Any)
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b = List(Str)
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a list of Strings
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c = List(Instance(Person))
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d = List([1,2,3], Int,
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Dict Traits
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sig: Dict(key_type, value_type)
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a = Dict
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b = Dict(Str)
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keys are strings
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c = Dict(Str, Float)
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Instance Traits
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class Person(HasTraits):
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class Family(HasTraits):
dad = Instance(Person, args=())
mom = Instance(Person, args=(), kw={'first_name': 'Jane'))
son = Instance(Person)
daughter = Instance('Person') # forward reference
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if you don't specify default value of instance, then the object will be None
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e.g. son will be None
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traits heavily uses magic methods, like _default
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Dynamic Defaults
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due_date = Date
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def _default_due_date(self):
return date.today() + timedelta(days=7)
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Properties
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class Rectangle(HasTraits):
width = Float(1.0)
height = Float(2.0)
area = Property

def _get_area(self):
return self.width * self.height
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cached_property decorator
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area = Property(depends_on=['width', 'height'])

@cached_property
def _get_area(self):
return self.width * self.height

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validation
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Range
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Enum
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width=Enum(1.0, 1.5, 2.0, 5.0, 10.0)
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height = Enum(values='allowable_heights')
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allowable_heights = List([0.5, , 1.0, 2.0])
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String
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hexcolor = String('#FFFFFF', minlen=7, maxlen=7, regex='#[0-9A-Fa-f]')
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regex is anchored implicitly to endpoints
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General Validation
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create a new trait type
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class PositiveFloat(BaseFloat):
default = 1.0
info_text = "a positive float"

def validate(self, obj, name, value):
value = super(PositiveFloat, self).validate(obj. name, value)
if value > 0:
return 0
self.error("Error")
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TraitsUI
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cross platform
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solaris, linux, mac, windows
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cross toolkit
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Wx, Qt
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MVC
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Where HasTraits objects are the model
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Easy to write basic UIs
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Powerful enough to handle full blown applications
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If you specify a 'View' attribute on a HasTraits objects
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View('width', 'height', 'Item('area', style='readonly'))
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Informs TraitsUI
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VGroup, HGroup
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Vertical/Horizontal groupings
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view1 = View(VGroup(HGroup(Item('width', label='w'),
Item('height', label='h')
),
Item('area', style='readonly'),
)
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Editors
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view = View(Item('cheese'),
Item('condiments': editor=CheckListEditor()
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TextEditor
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options
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auto_set
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set the trait value on every keystroke
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enter_set
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set when enter is pressed
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password
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multi_line
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mapping
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maps strings to trait values
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evaluate
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a callable which takes text and returns value
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evaluate_name
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BooleanEditor
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ButtonEditor
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HTMLEditor
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format_text
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do simple plain text to HTML formatting
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SetEditor
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TitleEditor
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ShellEditor
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a python editor
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SearchEditor
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text editor which looks like a search box
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ValueEditor
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tree view of a dict for example
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ProgressEditor
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progress bar
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RangeEditor
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EnumEditor
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can be used even on non-enum types
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InstanceEditor
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CodeEditor
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wrapper around Scintilla
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ListEditor
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has a use_notebook option.
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CheckListEditor
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Edit boxes
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drop down
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checkboxes
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text
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Images and Icons
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ImageResource
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create an images directory
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pyface
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underlying layer between toolkit and traits ui
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from enthought.pyface.api import ImageResource
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image1 = ImageResource('weather-clear')
image1.create_image(size=(32,32))
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by default will look in 'images' directory
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can specify search_path
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will find weather-clear.bmp, weather-clear.png, etc
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TraitsUI icons
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image3=ImageResource('@icons:red_ball')
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class ImageViewer(HasTraits):
my_image = Image
view = View(
item('my_image', 'ImageEditor(), style='readonly'),
)
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Other Editors
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ComponentEditor
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used for Enable canvases and Chaco interactive plotting
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chaco plot
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SceneEditor
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Mayavi or TVTK scene in a view
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CustomEditor
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takes a wx or qt control and embedds it.
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HistoryEditor
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ScrubberEditor
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PopupEditor
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TimeEditor
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DateEditor
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date/calendar
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ColorEditor and RGBColorEditor
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FontEditor
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FileEditor and DirectoryEditor
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ArrayEditor and ArrayViewEditor
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Table Editor
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columns
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ObjectColumn is a trait associated with an object
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ObjectColumn
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ExpressionColumn
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computes a value in the namespace of the object
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ListColumn
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CheckboxColumn
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filters
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columns_name
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menu
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search
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edited
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deletable
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auto_add
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TabularEditor
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TableEditor loads the full list into mem
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TabularEditor loads only the displayed objects into mem
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requires TabularAdapter
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TreeEditor
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Back to Traits
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Notification
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each trait has a bunch of listeners
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1 static listener
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def _volume_changed(self, old, new)
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a bunch of dynamic listeners
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on_trait_change
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can be used as a decorator
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on_trait_change can launch a new thread for the listener
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dispatch="new"
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_students_changed
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students is a List
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the entire class has changed
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_students_items_changed(self, event):
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when items are changed
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Extended Trait Names
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item1.item2
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item1:item2
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[item1, item2]
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item1[]
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anytrait
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+
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Delegation
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Kind of like a foreign key
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last_name = DelegatesTo('parent', 'last_name')
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update to last_name updates the delegated object (as well)
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Prototyping
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last_name = PrototypeFrom('parent', 'last_name')
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update to the object's last_name doesn't change the prototyped object
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Back to TraitsUI
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arguments
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pg 83 of the handout. :-)
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Views have traits
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height, width
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x, y
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resizable
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scrollable
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title
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...
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Groups
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padding
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height/ width
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...
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Item
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height / width
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e.g. 50%
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resizable
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springy
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full_size
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Subclasses
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HGroup / VGroup
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HFlow
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HSplit
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Tabbed
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vGrid
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Items subclasses
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Label
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Heading
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Spring
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Custom
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Readonly
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UItem
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UCustom
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Don't use Themes!
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Controllers / Handlers
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Add to views
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Add subclass of Handler object to view using handler= kwargs of a View
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Or could add as an option to edit_view() method
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Allows you to react to view changes
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Or...
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ModelView
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Controller can have a View
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more resources
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svn.enthought.com/enthought/wiki/Traits
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code.enthought.com/projects/traits/documentation.php
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A Long Pinax Tutorial
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Intro
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Daniel Greenfeld
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author/instructor for holdenweb
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pydanny
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James Tauber
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history
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2008 James Tauber decides to stop repeating himself
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Integrate numerous pluggable django apps
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Install
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python scripts/pinax-boot.py pinax_tutorial
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Core Components
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Accounts
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Avatar
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Email Address
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Language
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OpenID
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Password Management
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Signup
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Closed Sign-up
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Private Beta
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Optional Email Address
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Timezone
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Groups
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containers with user membership and provides content
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Examples
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Tribes
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wiki, photos
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Projects
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Tasks, wiki
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Guilds
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events
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Static Media Handling
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css
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images
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javascript
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Project vs Pinax Theme vs app level
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seperation of static media from user-contributed media
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build_static management command
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Pinax Projects
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Overview of starter projects
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boilerplate code
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scaffolding to get started more quickly
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already integrated apps
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basic_project
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social_project
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wiki, blog, etc
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code_project
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software management
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company_project
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New
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0.9alpha
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static content + blog
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static_project
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no models
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just template code
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pinax-admin clone_project -l
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pinax-admin clone_project social_project tutorial
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settings.py
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Pinax specific settings
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site_name
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STATIC_URL / STATIC_ROOT
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site developer's media
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local_settings.py
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set env for things like databases, debug, media locations
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Modifying core pinax apps
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Profiles
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frequently extended
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generally kind of site specific
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AUTH_PROFILE_MODULE = "profiles.Profile"
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need foreign key to django.contrib.auth.User
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before you modify
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can you accomplish change with:
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CSS
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Javascript
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don't make changes in pinax itself
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django-admin.py startapp profiles
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Adding Django Applications
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just install the package into the virtualenv
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Modification of templates
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customize templates, don't replace them
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Themes in Pinax
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PINAX_THEME="default"
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base.html
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theme-level look and feel
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site-base.html
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customizations
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django-avatar
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default uses Gravatar
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pros
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gravatar follows a user account name across the internet
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default avatar everywhere
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AVATAR_DEFAULT_URL = STATIC_URL + "some.png"
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AVATAR_GRAVATAR_BACKUP=False
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django-groups
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Groups containers with user membership and content
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base model on which to build your group app
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a way to do all your url routing so you get to the right content objects for the group
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group apps can be content objects belonging to other groups)
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from groups.base import Group

class Tribe(Group):
members = models.ManyToManyField(User, related_name="tribes", verbose_name="members")
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in the urls.py of the tribes app, you build bindings
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group aware apps
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# in urls.py
bridge = ContentBridge(Tribe, "tribes")

urlpatterns += bridge.include_urls("topic.urls", r"tribe/(?P<group_slug>[-\w]+)/topics/")


urlpatterns += bridge.include_urls("wiki.urls", r"tribe/(?P<group_slug>[-\w]+)/topics/")
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a content app would need:
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def tasks(request, group_slug=None, template_name="tasks/task_list.html", bridge=None)


if bridge:
bridge.get_group()
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if group:
tasks = group.content_object(Task)
group_base = bridge.group_base_template()
else:
tasks = Task.objects.filter(object_id=None)
group_base = None
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adding Content objects is simple
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plugin via ContentBridge in urls.py
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template extension
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{% extend group_base|default:"site_base.html" %}
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Look at sample_group_project for more details
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django-uni-form
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usable outside of pinax
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Section 508
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Rules for making technology accessible by individuals with disability
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Easy to impliment if you know how
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Doesn't force software to be accessible to the disabled
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$170 billion industry
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django forms rock
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but they are generally rendered as tables
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tabular forms are allowed in section 508... for tabular data, not for form elements
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django uni-forms
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django forms docs + template tag + uniform css/js forms library
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{% load uniform_tags %}
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<form = class="uniform">
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action handlers
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Static media
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{{ STATIC_URL }}
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points to build_static management dir
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SERVE_MEDIA
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for development
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build_static
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--dry-run
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don't copy, but show what would be done
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--link
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create symlinks rather than copy
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if using 0.7, the command is 'build_media'
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requires TEMPLATE_CONTEXT_PROCESSORS
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be sure to use RequestContext in the view
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e.g.
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<link href="{{ STATIC_URL }}css/polls.css" rel=stylesheet type="text/css"/>
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STATICFILES_DIR = [
os.path.join(PROJECT_ROOT, "media"),
os.path.join(PINAX_ROOT, "media", PINAX_THEME),
]
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Javascript/Jquery/Pinax
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Pinax has an opinion
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you can still use YUI, Mootools, or plain old Javascript
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{% block extra_body %}
<script type="text">
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django-ajax-validation
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alex gaynor
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does validation via ajax
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in urls.py
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django-pagination
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community / communicate
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don't be "that guy"
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be friendly
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be patient
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operating system and version of python
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use a paste server
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what the hell is a gblock?
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database storage of a field
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Hacking the Social Web
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Identity
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oauth
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authorization
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openid
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authentication
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@mjmalone
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relationships
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Google OpenSocial
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activity
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RSS
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ActivityStreams
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open stack
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democratize
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decentralize
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social web
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built entirely on HTTP (1.1)
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need to know it inside and out
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python stack
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http
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json
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simplejson
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xml
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atom
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feedparser
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html
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html5lib
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uri
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cgi
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urllib
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urlparse
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Identity
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OpenID
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decentralized mechanism for single signon
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allows single pw to be used across multiple sites
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about 500,000,000 accounts enabled with openid right now
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identifier
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an HTTP URI or an XRI
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relying party
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rp
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relies on a third party to prove ownership of an identity
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openid provider
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allows people to log in from their auth
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Just a URL
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e.g. http://stu.mp
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Steps
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auth provides identity
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relying party discoveres openid provider
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can redirect
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Using Yadis discovery
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discovering services associated with an URI/XRI
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X-XRDS-Location
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<meta http-equiv="X-XRDS-Location"
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curl -I -H "Accept: application/xrds
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<link rel="openid.server"
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<link rel="openid2.provider"
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relying party redirects user to openid provider
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authenticates
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Openid provider redirects user back to the original site
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implimentation tips
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usedd openid_identifier as the html form identifier in HTML to allow browsers to autocomplete
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trust relationship between provider and relying party
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pre-established association
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diffie-helman key exchange
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contact the openid provider directly to verify
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being a provider
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1. decode the request and determine its nature
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2. Decide how to respond to the request
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server can respond automatically to some request types by passing to server.handleRequest
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3. encode a response
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wrap it up with yadis discovery
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xrds capabilities document on your server that points to you provider
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openid example code
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github/mmalone
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OAuth
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protocol for secure password free api
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delegates authorization to third party
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problems addressed
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share private resources to third party without giving out creds
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allows apis to keep track of third parties accessing private resources
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allows users to revoke access to third parties
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if giving out password, can't take password away from one a single identity
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standard interface for
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GData
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OpenSocia
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Facebook
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twitter
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going through IETF draft spec
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has potential to replace Digest auth
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password anti-pattern
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exposes pw to third parties
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forces third parties to store the user/pw in plain text
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no reverting permission
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no support for other auth mechanisms (openid)
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teaches users to be fished
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terminology
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credentials
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unique key and shared secret
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client credentials
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identify an invidual client
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temporary credentials
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identify an authorization request from a client
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kind of like a "dmv number" tracking a request through the process
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token credentials uniqueeely identify a client accessing the server on behalf of a resource owner
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three legged OAuth
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3rd party sends a signed request to the api for a request token
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3rd party redirects user to API provider asking for access
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user grants access and is redirected back to 3rd party
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3rd party sends a signed request to the api to obtain authorized access tokens
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two legged OAuth
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problems
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no way to delegate tokens
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Allowing TwitPic to post on behalf of Tweetie
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no way to programmatically register client
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HTTP body is not signed
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user experience from non-web apps is clunky
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endpoints are specific to an API and server
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no standard for specifying permission
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implimenting the client
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python-oauth2
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Portable Contacts
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address books
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defines an xml and json serialization of a vCard
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simple restful api
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protected by OAuth
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discovery uses XRDS-Simple (Yadis) like OpenID
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part of opensocial stack
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Integrated with OpenID and OAuth in Gmail
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required endpoints
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/@me/@all
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/@me/@all/{id}
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return contact information for the provided id if such
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/@me/@self
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return contact info for the authenticated user
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filtering
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filterBy
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filterOp
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filterValue
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sorting
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pagination
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presentation
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fields
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limit the fields client would like returned
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format
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xml or json
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Problems addressed
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common access pattern and contact schema
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minimal complexity with the lightest possible tool chain requirements
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password
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Activity Streams
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express activities in such a way that you don't need to know the other websites
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supported by google myspace....
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friend-feed tracking is a pita
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anatomy of an activity
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actor verb object context
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Joe favorited a photo on flicker.com
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verbs and object types are defined by IRIs
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there is a standard set, but you can create your own
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OEmbed
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format for allowing an embedded representation of a URL on third party sites
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allows a website to display embedded content
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request
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url
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you're wishing to embedded
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maxwidth
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max width of the embed
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maxheight
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format
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xml or json
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response
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type
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version
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title
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author_name
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author_url
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provider_name
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provider_url
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cache_age
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thumbnail_
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discovery of oembed
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<link rel="alternate" type="application/json+oembed"
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drop the oembed object into an iframe
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hosted on another domain
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http://oohembed.com/
hideksmiletris bookmark
Django Deployment Workshop
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Intro
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Jacob Kaplan Moss
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RevSys
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github.com/jacobian/django-deployment-workshop
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infrastructure for scaling
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LiveJournal Backend: Today
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http://danga.com/words/2007_06_usenix/
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brad fitzpatrick
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Simplified deployment stack
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nginx
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apache
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mod_wsgi
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pgpool
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postgres
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database and web
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both are big consumers of memory and I/O
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fumblerooski.org is his demo app
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Setup Django/App dependencies
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he uses buildout
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could use pip
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packages he treats as deps
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Fabric
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BeautifulSoup
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psycopg2
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Unipath
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gcharts
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django-piston
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memcached
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Setup Postgres
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/etc/postgresql/8.4/main
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invoke-rc.d
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postgresql.conf
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listen address
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tweak max_connections
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pg_pool holds 40 connections
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2 web servers
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plus a handful of others
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pg_hba.conf
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local host trust
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host trust
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Setup Apache & mod_wsgi
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wsgi vs mod_python
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memory consumption far less
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more consistent
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he prefers apache as the app server
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light server in front of heavy backend app server
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lighttpd / nginx
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used for media and front end servers
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SSL
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apache
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heavy processing
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ServerTokens ProductOnly
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load test tool
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siege
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only really needs
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mime_module
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alias_module
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wsgi_module
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and that's it for small deployments
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For larger deployments, redudant
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some alternatives for repeating tasks across hosts
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fanout
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bash script for repeating stuff
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capistrano
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ruby
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fabric
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python
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paver
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python
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config management
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puppet
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chef
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cfengine
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bcfg2
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Load balancers
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even on a single machine
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"spoon feeding problem"
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fat pipe
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server will almost always be more powerful and have better bandwidth than client
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server resources basically wasted while waiting on pipes to clear out
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front end server should be able to handle lots of connections
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nginx can easily out handle connection compared to apache
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and have output buffering
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allows for easy scaling
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sure it's single machine now, but how about tomorrow?
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lighttpd
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tends to prefer for static media
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although static media may be better on cdn
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perlbal
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http://www.danga.com/perlbal/
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can dynamically add new backends without requiring a reload
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nginx
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config file is simple and clean
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end lines with semis
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leaf
proxy_set_header Host vhost.servername.com
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can add weights to backends
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can specify 'sticky' load balancing
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although if you need it, you're probably doing it wrong
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Caching
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"Most of the time, performance is an excercise in caching"
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"The only excuse for not using memcached is if you've found something faster, in which case I want to know about it"
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"The great dict in the sky"
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Good caching strategy is the difference between a good site that runs and a site that fails
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he prefers "the google" approach to memcached over the "facebook" approach
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run it everywhere
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as opposed to on large clusters
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Sets up memcached on all web servers, monitoring servers, etc
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not on db servers, or other memory constrained platforms
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Database connection middleware
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allow database failures/rollover without changing database code config
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automatic failover
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connection pooling
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pgpool2
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run it on every web machine.
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lightweight
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all in io
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check out the pgpool/etc-default-pgpool
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connection_cache = true
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num_init_children = 2
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max_pool = 20
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"most big extended outages aren't what you wrote, it's what you plugged your stuff into"
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Database redundancy
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live backend
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slowny
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some other tool
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warm standby is normally good enough
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master fails
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you bring up the slave
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wal shipping
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before it writes to disk, dbs write to the write ahead log (WAL)
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copy the WAL to the slave and replay
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mkdir a WAL file archive directory
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postgres config file
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archive_mode=on
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archive_command = 'rsync ...'
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copy locally, then remote copy them when syncronized
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using rsync so it's atomic (or at least "fixed")
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force an archive of a WAL file
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select pg_switch_xlog();
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WAL archiving allows for "snapshot in time" capability in a db
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apt-get install postgresql-contrib
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creating the db
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psql template1 -c "select pg_start_backup('baseline');"
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in_cron
hideksmiletris
Keynote: Building the Python Community
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Steve Holden
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Lots of shout outs and thanks
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produce amazing software
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blip.tv/pycon
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python.mirocommunity.org
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"PSF - Shovelling crap so you can keep doing what you are doing"
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Diversity
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formal diversity statement
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associate membership
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financial support
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Foundation's goal:
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broaden python's popularity and win mindshare
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"Python: the friendly language"
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"You may be weird but you'ree my kind of weird"
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Keynote: GvR
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"I hope there won't be a python 4 in my lifetime."
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2.7 will likely (hopefully) be the last in the 2 series.
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Nothing makes python especially suited for men, so of course it's suited for girls.
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"The complete freedom of Ruby syntax kind of gives me the creeps"
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Realtime web
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Alex Gaynor
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http://alexgaynor.net
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slideshare for the slides
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Leafy chat
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Cometd proxies to twisted freenode
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it all sort of works
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but wasn't pretty
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irc i the same proces as comet (doesn't really scale)
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long lived connections had to go to the same server
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new functionality
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added it to the server, the client and the UI lib
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DjangoDose
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twisted, orbited, django
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stompmq
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live feed of everything that was going on in twitter
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plus it's own trending topics
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client joins a morbidMQ, on initial connect, it joins an initial channel and a feed channel
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feed channel spits out json for tweets when they come out
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good when all clients are receiving the same channel
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no individualized connections
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same as leafy chat, no isolation between coment and twitter
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Hurricane
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producers and consumers
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coment producer/consumer
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Long polling with jQuery
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Tornado Server
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multiprocessing lib to have producers and consumers run concurrently
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Application state was in memory
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They ended up rewriting comet producer/consumer a lot
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never really got abstractions right
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which user is which
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how do you know what messages go to what users?
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A lot more data and more users
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DjangoDose
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Redis
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key/value store
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with real datastructures, lists, sets
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hashes
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but all data has to be able to store in memory
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buckets for data
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pycon-feed
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json
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json
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json
leaf
json
leaf
...
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hourly buckets
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json
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json
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json
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has a blocking pop operation
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orbited proxies to a twisted daemon
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twisted daemon uses a blocking operation on redis to be notified
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lessons learned
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async is hard
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generator based async programming rocks
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VisTrails
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David Koop
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University of Utah and VisTrails, Inc
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vistrails.org
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Scientific Workflow and Provenance System
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vtk
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visual workflow
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provenance
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knowing the lineage of something helps validate (art for example)
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in science, how you got there can be more important than the actual results
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old solution
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lab notebooks
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dates
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annotations
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observed data
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new problem
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massive data
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new solution
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vistrails workflow
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execution provenance
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logging
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design provenance
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version tree
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software
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mac/linux/windows
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pyqt
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integrates with lots of other visualization engines
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Packaging and Dependencies And Stuff
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Ian Bicking
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"Everything is flawed"
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"We should know our own flaws"
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pseudo-Feature
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No dependencies
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installation
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not a lot of code to read
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stuff breaks less often
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who owns it
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like the comfort food of libraries
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For work to scale, we need dependencies
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versions
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major.minor.bugfix
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contracts are a fantasy
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__all__ defines what is 'public'
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but only works with 'from module import *
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good programmers don't do import *
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The cloud
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get a new server on demand, in minutes
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server is disposable
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servers are always identical
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"Ad hoc system administration is like programming at the Python shell"
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biggest thing source control does is 'commit'
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a point of reflection and analysis of "what have I just done"
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toppcloud
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pushing projects "to the cloud"
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Database Scalability
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Jonathan Ellis
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of mozie
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now on cassandra
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scaling
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money vs operations per seconds
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throughput
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It scales but...
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have to keep adding people to operations
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when the netapp runs out of capacity, we're screwed
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it's not fast
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major headache
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just gotten worse in 10 years
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b-tree database indexes
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web apps have much bigger user populations
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Some Band-aids
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mitigate amount of work the db has to do
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perhaps Solid State Drives
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moore's law
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caching
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memcached
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ehcache
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If you are relying on cache for decent performance, you have to make sure a cache machine never goes down (and certainly not all of them at once)
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Cold start problem
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Consistent hashing
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libketema for memcached
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consistent hashing
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cache coherence strategies
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write through
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explicit invalidation
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implicit invalidation
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problem though... cache (set) invalidation
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set invalidation 2
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use a hashed prefix
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if you want invalidate the set, invalidate the prefix
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cacheing often thought of as 'read' hotspot problem
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Can be used (with caveats) for write caching
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Scaling Reads
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replication
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multi-master
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syncronous = slower
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complexity
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PGCluster
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Async master/slave
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easiest
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mysql replication
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slony, londiste, WAL shipping
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tungsten
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mongodb
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redis
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Async multi-master
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conflict resolution
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Bucardo
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MySQL Cluster
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Tokyo Cabinet
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async can lose data
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if you're writing to a node and it goes down, data gets lost
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does not scale "writes"
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Scaling writes
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Each machine only handles a subset of data
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horizontal sharding
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subset of records on different hosts
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vertical sharding
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subset of info on different hosts
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sharding
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vertical/horizontal
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which server gets which key?
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consistent hashing
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or central-db that knows what server owns a key
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makes a machine easier
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partition with replication
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ends up needing lots of machines
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lots of complecity
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NoSQL
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Distributed (partitioned, scalable)
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cassandra
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HBase
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Voldemort
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not distributed
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redis
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couchdb
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Two famous papers
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"How can we build a distributedd database on top of gfs"
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Dynamo: How can we build a distributed hash table appropriate for the data center
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Cassandra: Dynamo style replication
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Maximize your program's Laziness
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cheapest, fastest and most reliable components of a computer system are those that aren't there - Gordon Bell
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review of laziness
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in other langs:
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haskell
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really lazy, nothing is calculated until it's needed
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scheme
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introduces laziness with declaration of promise
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delay () command
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in python
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we're dealing with iterators and generators
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potentially infinite length
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or deferals using '__call__()' or __getitem__ overloading
hidelicq
Ring of Python
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Python interpretters
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cpython
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many platforms
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many extensions
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the mainstream python
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python3
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struggling for breakthrough
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stackless
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microthreads
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massive concurrency
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psyco
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c-extension specializing compiler
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not really a varient
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Cython
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writing extension modules mixed with C
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derived from pyrex
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Unladen Swallow
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LLVM-JIT
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Jython
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glues python into java and the JVM
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threading minus the GIL
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IronPython
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full .NET available to python
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integrates with Silverlight. Silverlight can call python
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the real evil?
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google
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data control
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apple
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app control
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Jonathan Zittrain: The Future of the Internet and how to stop it
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Google Talks
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Parrot/Pynie
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PyPy project
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true sandboxing
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cpu, ram, io
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python tracing
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jit
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garbage collectors
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can reduce memory usage to more than 50% of cpython's
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speed and competition
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it's not just about competition
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developers cooperate
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speed isn't everything
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not just how fast at executing, but what additional features allow you to build a better project with better architecture
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deployment and cooperation
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main differentiator is deployment
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software is 'deployed' now, not 'built' anymore
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deployment
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EC2
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App Engine
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private
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servers
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data
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clouds
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networks
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hybrid deployment
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interpretter diversity
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cross interpretter tools
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testing
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Selenium
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Hudson
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buildbot
leaf
unittest
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testresources
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nose
leaf
py.test
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packaging
leaf
pop
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distribute
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distutils2
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buildout
leaf
virtualenv
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python bridging to
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C
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Java
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C#
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Javascript
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spiermonkey
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Lua
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Lunatic Py
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C++
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boast
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but no python-to-python
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execnet
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remote rpc
leaf
import execnet

group = execnet.Group()
group.makegateway()
group.remote_exec("import os; channel.send(os.getpid())")
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preso
Arrow Link
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pritzy
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adobe air app
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preze
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Python Patterns
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Pattern definition
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find a class of problems similar to the one you have
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solve the class of problem so that specific problem is also solved
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a pattern must have a 'name'
leaf
http://www.aleax.it/pycon_ppp.pdf
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(04:35:01 PM) zellyn: btw, http://www.aleax.it/goo_pydp.pdf has lots of actual python patterns with code.
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does python have patterns
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no patterns
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they haven't looked
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no problems
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no life
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Patterns help the field "up their game"
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work is a connected mesh of activities
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find problems, opportunities, connections
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identify system structure
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invent/discover possible solutions
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experiment to evaluate
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test/deploy/deliver/distribute document
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what other kinds of patterns beyond just design
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analysis
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find value opportunities
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architecture
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large scal overall system approaches to let subsystem cooperate
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human experience
leaf
leaf
hide
testing
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how to verify system quality
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cooperation
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how to help people to work together
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deliver/deployment patterns
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pythonic pattern
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uses python
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well adapted to python strengths
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dealing with python-specific issues
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e.g.
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http://www.aleax.it/goo_pydp.pdf
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pythonic template method
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self-delegation
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classically via inheritance
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python aspects
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overriding data
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Queue
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ABC (or mixins) with organizing methods
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factored-out hooks (via delegation)
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organizing class can use runtime introspection to find hook-methods
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all of the above
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Dependency injection as a template method
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factored out template method
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callback dispatch
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inect the hooks (callables) as args
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Works best with first-class callables
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what's an idiom
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small-scale, technology-specific, common choice of name, arrangement or procedure
leaf
e.g. brick-overlap wall
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if __name__ == '__main__':
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really only makes sense in python
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while(*dest++ = *source++) {}
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only really in C/C++
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anti-pattern and anti-idioms
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waterfall, analysis paralysis, moral hazard, groupthink
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polling
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python specific
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def __init__(self, this, that):
super(Cls, self).__init__(this, that)
leaf
for string_piece in many_pieces:
big_string += string_piece
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sum(list_of_lists, [])
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Pattern *languages*
leaf
hidelicq
Non-standard use of Django
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Using something other than base django functionality
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Using Jinja with Django
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Jinja2
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an alternative template
leaf
makes different tradeoffs from django's template
leaf
sometimes Jinja2 makes sense
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they wrote django_ext
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basically just implimented their own shortcuts
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Not using Django.contrib.auth
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why not?
leaf
when using it will be more difficult than not using it
leaf
e.g. writing a facebook app
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facebook apps
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you don't render html
leaf
you render fbml, which facebook assembles and renders for the user
leaf
user -> facebook -> django -> facebook -> user
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no such thing as user registration
leaf
you already have unique id
leaf
didn't even attempt to make it fit the django.contrib.auth paradigm
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Advantages
leaf
straigtforward code with clear intent
leaf
didn't waste time trying to shoehorn Facebook user ids into the username field
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reduced overhead
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still got the django stack
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Not using the ORM
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integrating with complex legacy databases
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using a database that the ORM doesn't support
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(non-relational db)
leaf
you're talking to an API, not a DB
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Why not write a db backend
leaf
won't have time
leaf
might not make sense
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Post JSON over HTTP
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talks to a postgresql
leaf
returns a JSON response
hide
Using something out of django in a non-web context
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using django forms in pylons
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initially
leaf
no form library
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manual post and validation
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looked into
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to get it to work
leaf
turn of Django's I18n handling
leaf
new form base class to coerce WebOb MultiDicts into a QueryDict
leaf
a genshi wrapper to allow the form to be generated
leaf
settings.
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Why use ORM Standalone
leaf
you like the API
leaf
you have apps
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call settings.configure with db info
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Using WSGI middleware with Django
leaf
started with repoze
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repoze.bitblt
leaf
scales images
leaf
caches
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repoze.squeeze
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merges JS/CSS automatically based on statistical analysis
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repose.profile
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aggregates python profiling data across all requests and provides an HTML UI for viewing the data
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Typical .wsgi
leaf
from django.core.handlers.wsgi import WSGIHandler
application = WSGIHandler()
leaf
from django.core.handlers.wsgi import WSGIHandler

from repoze.profile.profiler import ... as P

application = P(WSGIHandler(), log_filename='/tmp/log'))
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other non standard stuff
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yardbird
leaf
irc using django's url mapping to match messages and views to handle the callback
leaf
djing
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presenter
leaf
Twitter: @ericflo
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www.florenzano.com
leaf
mochimedia.com/jobs.com
hide
Friday Evening Lightening Talks
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What an Open Space Lawyer actually does
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Van Lindberg
leaf
van.lindberg@gmail.com
hide
Jacobson vs Capson
leaf
as of today open source really has teeth
leaf
today it settled!!
leaf
100k settlements +injunctions
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Copyright law + software == steak + ice cream
leaf
two great tastes that don't necessarily taste good together
hide
Derivative works
leaf
open source licenses reach as far as the copyright does. How far does it reach?
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derivative work analysis needs to lknow the
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law
leaf
code
leaf
community
hide
The Next Big Programming Book
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Greg Wilson
leaf
Hates his mac
leaf
thirdbit.com
leaf
Beautiful Code author
leaf
Beautiful Architecture
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architecture books
leaf
show you importance of architectures
leaf
don't really show you good examples
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Two competing products
leaf
describe their code difference
leaf
Architectures
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Don't Write Big Applications
leaf
MosheZ
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"Big"
leaf
Bank web site
leaf
OCR
leaf
Music clip auto-programmer
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Strategic Choices
leaf
language
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structure
leaf
modular code generally isn't
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better:
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Web
leaf
Json-rpc
leaf
xml-rpc
leaf
restful
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DB
leaf
mysql
leaf
postgresql
leaf
oracle
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non-sql
leaf
file system
leaf
cassandra
leaf
couchdb
leaf
Write lots of small processes with loose integration
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What's new in coverage.py
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Ned Batchelder
leaf
nedbatchelder.com
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New HTML reporting
leaf
coverage run mycode.py
leaf
coverage html
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New: Branch coverage
leaf
coverage run --branch
leaf
can detect where if's don't get evaluated
leaf
Now runs on Python 2.3 - 3.1
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much faster
leaf
tracing function is in C
leaf
don't trace stdlib
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XML output for Continuous Integration
leaf
Cobertura compatible
hide
Soon:
leaf
.coveragerc
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Upcoming
leaf
new nose and test.py plugin
hidebookmark
Python Docx
leaf
bullshit free way to create, edit and read MS Word Documents
leaf
@mikemaccana
leaf
github.com/mikemaccana/python-docx
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Can extract plain text of documents
leaf
found popularity with angry unix guys
leaf
document types
hide
can add and delete items anywhere within the document
leaf
search + replace
hide
Serving Suggestions
leaf
Auto-build a word doc
hide
ActiveState
leaf
new site
leaf
new book
hide
json api
hide
recipes script
leaf
on pypi
leaf
code.activestate.com
leaf
Trent Mick
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Progress Database
leaf
Danial holth
leaf
bitbucket/dholth
leaf
progress sqlalchemy dialect
leaf
not as hard as you might think
hide
Better ways to debug the Cpython runtime
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Dave Malcolm
leaf
fedora maintainer
leaf
sees lots of python runtime errors in extension modules
leaf
wrote a gdb7 extension (in python)
leaf
shows python line numbers of the C stack frames
leaf
and basic python data structures
leaf
python-gdb
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Voice recognition with Python
hide
David Huggins
leaf
dhuggins@cs.cmu.edu
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Speech recongition
leaf
read some audio and decode it
leaf
????
leaf
profit
leaf
cmusphinx.sourceforge.net
leaf
python-pocketsphinx
leaf
import pocketsphinx as ps
leaf
hide
Ubuntu one
leaf
file sharing service
leaf
wants help for porting it to Windows platform
leaf
lucio.torre@canonical.com
hide
Saturday Morning Lightening Talks
hide
haystack django search
leaf
custom search interface
leaf
for django
leaf
doesn't require third party apps to be search aware
hide
uses standard backends
leaf
xapian
leaf
swishe
leaf
...
leaf
good test coverage
leaf
decent docs
hide
twisted needs you
hide
ulitimate quality development process
leaf
bug
leaf
patch
leaf
review
leaf
merge
leaf
bugs need reviewing
leaf
python 3 incompatibility warnings
hide
python translation party
leaf
Trent Nick
leaf
lib3to2
leaf
then lib2to3
hide
Pycon by the numbers
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1025 currently
leaf
largest pycon ever
leaf
about 10% female
hide
State of Ironport Keynote
leaf
Dino Viehland
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IronPython 2.6
leaf
ctypes
leaf
optional support for sys._getframe
leaf
sys.settrace/pdb
leaf
new interpretter
leaf
Contributions now able to be submitted upstream
hide
New website
leaf
ironpython.net
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Coming up
leaf
improved import time
leaf
other performance tweaks
hide
.NET 4.0
leaf
C#/VB.NET can call IronPython code directly
leaf
IronPython Tools for Visual Studio Prototype
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Future
hide
FePy 2.7
leaf
end of 2010
hide
FePy Tools for Visual Studios
leaf
end of 2010
hide
FePy 3.2
leaf
end of year 2011
hide
State PyPy
hide
last year
leaf
speed / JIT
leaf
Feb - merged experiments into mainline
hide
Compiles to assembler
leaf
Feb
hide
Sept 2009
leaf
First able to run non-trivial programs
leaf
Now runs a dozen or so performance tests nightly
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now
leaf
Jit is fairly good
leaf
can consume a lot of memory
leaf
can compile code too many times
leaf
Garbage collection is pretty good
leaf
runtime algorithms are not a polished as Cpython ones (e.g. strings, regexs)
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future
leaf
release march 2010
leaf
first pypy release to contain a working JIT
leaf
morepypy.blogspot.com
leaf
pypy.org
hidelicq
Mark Shuttleworth Keynote: Things Open Source could do better
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Cadence
leaf
Time based release has real benefits
leaf
focus on stuff that is important now
leaf
the act of making a release energizes community
hide
some groups don't kick in unless there is a release
leaf
publicity
leaf
testing
leaf
translation
leaf
if you know there will be a release "soon", reduces the motivation to rush bad code in
hide
others are picking it up
leaf
kernel is unofficially on a cadence
leaf
6 month incrimental release
hide
2 year big releases
hide
hw guys:
leaf
18-month to 2 year
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installers and distributors:
leaf
2yr - 4 yr
leaf
2 year cycle is a good sweet spot
hide
Quality
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good distributed revision control is important
leaf
merge
leaf
branch
hide
automated testing
leaf
encourages better community participation
leaf
allows maintainers to feel more comfortable accepting patches
leaf
puts all patches on a (more) equal footing
hide
automated landings on trunks require process
leaf
commit access to trunk stripped from everyone but a robot
leaf
robot enforces that all tests pass
hide
Code review
leaf
allow people to review a branch
hide
on call reviewer
leaf
people can take any patch less than 800 lines
leaf
review the code
leaf
commit
hide
have good maintenance policies
leaf
don't blur lines between releases
leaf
stable release update policy
hide
automated crash reporting system
leaf
collect what package managers say they need
hide
Design
leaf
What will it take to get people to love this software
leaf
They are "an infection point" for open source
leaf
design is a different discipline with different skills
leaf
"when we stop working on something when it works for us, we are effectivly saying that we are the most important person in the universe and that users don't matter"
leaf
look at your software through a child's eye
leaf
they shouldn't need your help when you're in the room, they need your help when you're not in the room (programming the thing)
hide
iatana team
leaf
zen term for sphere of consciousness
hide
ASync IO Demystified
leaf
Blocking IO Review
hide
Non-blocking I/O
leaf
still synchronous
leaf
an i/o operation that only runs if it wouldn't block
leaf
returns errno EWOULDBLOCK if it can't read/write any data
leaf
returns the count of bytes read
leaf
has potential to fill kernel buffers, which would stop kernel from collecting more data
leaf
to turn fd into non-blocking io
hide
in python
hide
fcntl
leaf
ofl = fcntl.fcntl(0, fcntl.F_GETFL)
leaf
fcntl.fcntl(0, fcntl.F_SETFL, ofl, ofl | os.O_NONBLOCK)
hide
I/O Multiplexing
leaf
the kernel offers poll()
leaf
you ask for which FDs are ready for I/O
hide
Event driven I/O models
leaf
readiness of an fd for I/o is an event
hide
libs and frameworks support attaching a callback for these events
leaf
context objects can be anything that has a ready() method associated with it
hide
it's still syncronous though
leaf
kernel's buffer don't get flushed until you read the buffers
hide
so if your thread of execution blocks
leaf
cause of context switch
leaf
page faults
leaf
blocks on mutex or semaphore
leaf
or anything else, then I/O stops
leaf
called async though since it's async to your application code
hide
So why is it better?
leaf
better memory usage
hide
blocking I/O requires on thread of execution for each FD
leaf
large memory footprint
hide
drive lots of I/O
hide
non-blocking I/o services
hide
libev
leaf
pyev
leaf
more up-to-date
hide
libevent
leaf
pyevent
leaf
a bit dated
hide
frameworks
leaf
tornado
leaf
twisted
leaf
asyncore
hide
direct i/o
leaf
kernel given a pointer to a buffer space to write into
leaf
no kernel buffering and coping
hide
Sum up
hide
I/O readiness events occur async
leaf
handled syncronously though
leaf
increased scalability
hide
poll / epoll
leaf
10,000 file descriptors
leaf
how do you tell the kernel what you want done
leaf
don't necessarily want to pass array of 10,000 each time
leaf
poll / epoll pass the list 10,000 sockets once
hide
level triggered events
leaf
if an event happens, the fd is reported each time poll is called
hide
edge triggered events
leaf
only triggered when the event happens and subsequent requests don't get duplicated unless explicitly cleared
hide
eventlet
leaf
coroutine based system
leaf
hides async callback requirement
leaf
when kernel blocks, coroutine is called to allow you to go do other things
hide
Cooperative Multitasking with Twisted
hide
David Reid
leaf
dreid@dreid.org
leaf
Getting things done Concurrently
hide
Why is it needed
leaf
things will block...
leaf
but blocking is fine in moderation
hide
what will block?
hide
non-twisted networking
leaf
urllib&httplib
leaf
smtplib
leaf
memcache
hide
C extensions
leaf
db apis
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hard core crypto
leaf
File I/O
hide
Most of the time it will be your code
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for loop iteration
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twisted as alternatives to most of these though
hide
twisted in 3 slides
hide
the reactor
leaf
infnite loop
leaf
event loop
leaf
while true:
stuff = wait_for_stuff(timeout)
if stuff:
check_reads_and_writes()
run_timed_events()
hide
deferreds
hide
data source reader
hide
returns a deferred
leaf
callback function for success
leaf
errbacks for failures
hide
timed events
leaf
reactor.callLater(10, do_stuff) # 10 seconds
leaf
reactor.callLater(0.0001, do_stuff) # run the code the next time it can be
hide
new loop
leaf
def do_stuff(data):
d = Deferred()

def do_later()
do_work(data.pop())

if not data:
d.callback(True)
else
reactor.callLater(0.0001, do_later)
reactor.callLater(0.0001, do_later)
return d
hide
twisted.internet.task.Cooperator
leaf
task scheduler
leaf
twisted.internet.task.coiterate
hide
twisted.internet.task.cooperate
leaf
similar to coiterate
leaf
def do_stuff(data):
def doterator():
for x in data:
do_work(x)
yield None

return cooperate(doterator())

task = do_stuff(someData)
task_d = task.whenDone() # the deferred
task.pause()
task.resume()
task.stop()
hide
your app code is going to block
leaf
iterating over your stuff is the big place where sync code blocks
leaf
iterating is easily broken up by timed events
leaf
twisted makes this easy
leaf
the apis are the building blocks for your task processing system
hide
Why?
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frequently
leaf
being able to do more stuff is sometimes more important than doing stuff quickly
hide
can't I just use deferToThread for python code
leaf
gil hates you
leaf
gil hates me too
hide
can't I just run code in seperate processes
hide
yes, look at Ampoule
leaf
launchpad.net/ampoule
leaf
even if you have a process pool, you probaby want the processes to do more than one thing at a time
hide
why not set callLater to 0?
leaf
you could potentially chain your loop and never yield to I/O
hide
references
hide
txRDQ
leaf
launchpad.net/txrdq
leaf
resizable dispatch queue
hide
Interfaces, Adapters, and Factories
leaf
design patterns mentioned in gang of four book
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usefulness of more Interfaces
leaf
competes with Abstract Base Class
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Adapter Pattern
leaf
converts the interface of a class into another interface that client expect
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Factor Pattern
leaf
organize and make easily configurable the places to obtain objects
hide
zope.interface/zope.component
leaf
one implimentation
hide
Two Protocols
leaf
class Orange:
def getcolor(self):
....
leaf
class Apple:
def __init__(self...)
self.color = color
leaf
two similar data objects that are speaking two protocols
hide
could if case them
leaf
brittle
leaf
special cases
leaf
could build an adpater object...
hide
better ways than:
leaf
ducktyping, detect methods
leaf
inheritance checking
leaf
something else, interfaces!
hide
tagging
leaf
provides meta info about the methods and attributes used
leaf
a single object may provide multiple interfaces
leaf
in some languages, interfaces are a workaround for lack of multiple inheritance
leaf
in python, it's just advisory
hide
Interfaces
leaf
seperates what can be done from how it does it
leaf
provides an API documentation
leaf
act as invariants
leaf
can be dynamic, so runtime registry associating objects
hide
from zope.interface import Interface
leaf
class iOrange(Interface):
"tasty plant"
def getcolor(): # no self
"docstring"
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classes "implement" interfaces
leaf
iOrange.implementedBy(Orange)
leaf
can be used with verify
hide
Adapters
leaf
methods and calls to an object
leaf
adapter connects to an adaptee object
hide
e.g. StringIO
leaf
adapts a string to File object
hide
not casting or coehersion
leaf
holds a ref to adaptee, and delegates to X
leaf
may not be fully substitutable
leaf
skinny adapter
hide
adapter registry
leaf
adapters can specify what an adapter can convert in and out of
leaf
a lookup resolution protocol
hide
could look in
leaf
config file
leaf
loaded modules
leaf
installed modules
leaf
some plugins directory
leaf
PyPI
hide
adapting from multiple interfaces
hide
multiple outputs
leaf
http request
leaf
report writing
hide
adapting from nothing
leaf
get a generic object providing a interface
leaf
object factory
leaf
going too fast to take notes...
hidebookmark bookmark ksmiletris
Mastering Team Play: 4 examples of composing python tools
leaf
Raymond Hettinger
leaf
urls
hide
Ordered Dictionary
leaf
bit.ly/a4pE6l
hide
Running Median
leaf
bit.ly/aAHWFl
leaf
NFA to DFA conversion
hide
quick review
leaf
lists and deques
hide
lists
hide
append, pop
leaf
efficient at right side
leaf
mutable
leaf
compact array of pointers
leaf
insert, but slow
hide
deques
leaf
like lists
leaf
double ended queue
leaf
append and pop efficiently from both ends
leaf
they do not support 'insert()'
hide
sets and dicts
leaf
fast O(1) lookup
leaf
hashable values
hide
frozen sets
leaf
hashable
leaf
allowing sets of sets
hide
sparse structures
leaf
use much more memory
hide
other
leaf
sorting takes n log n time
hide
tim sort
leaf
if the data already sorts
leaf
can be O(n)
hide
heapq tracks running minimums
hide
pushes and pops in O(log n)
leaf
partial sort
hide
bisect
leaf
uses O(log n) binary search
leaf
bisect.insert() is still O(n) because it inserts in a regular list
hide
Random Sampling without replacement
leaf
bit.ly/c2510i
hide
Lottery ball example
leaf
or decks of cards
leaf
distinct numbers with no repeats
leaf
no dup selections
leaf
multiple good algorithms
hide
two strategies
hide
lbyl
leaf
look before you leap
leaf
prevent duplicates by mutating the population list
leaf
population centric
hide
eafp
leaf
easier to ask forgiveness than permission
leaf
reject duplicates by remembering prior choices
leaf
sample centric
hide
preventing duplicates
leaf
need to be able to move items in and out
leaf
indexable
leaf
implies lists
hide
rejecting duplicates
leaf
need to be able to do fast lookups and unique values imply sets
hide
random.sample
leaf
does adaptive algorithm selection based on arguments
hide
Ordered Dictionary
leaf
Like a regular dictionary
leaf
rembers insertion ordered
leaf
maintain order when modifying
hide
easy to do badly
leaf
add a order list to to a dict subclass
leaf
list.remove on delitem becomes O(N)!!!
hide
deleting arbitrary items from a list takes O(N)
leaf
deleting elements from a double link list is O(1)
leaf
track the order of items
leaf
links can be deleted in O(1) time
leaf
OrderedDict
hide
Running Median
leaf
like a moving average
leaf
keep a large sliding window of data
leaf
when a new point is added, the oldest gets removed
leaf
sort the elements in the window
leaf
return the middle element
hide
obvious answers tend to fail for large data windows
hide
sort on every update
leaf
o(n log n)
leaf
slow
hide
quick select algorithm
leaf
O(n)
leaf
aspn cookbook
hide
decent solutions
hide
best published solution
leaf
O(sqrt n)
hide
subdivide the sorted data into equal sized pools
leaf
(sized to sqrt n)
leaf
to add a value, find target pool by searching the last element of each pool
leaf
update the target pool with simple insertion
leaf
rebalance the books so equal sized
leaf
good demos
hide
skiplist solution
leaf
O(log n)
hide
b+ tree solution
leaf
O(log n)
leaf
nondesterministic finite automata
hide
discrete finite automata
leaf
frozen sets allowed sets of sets
hide
C version
leaf
bit.ly/cgfoDc
hidelicq
Actors: What, Why, and How
hide
Donovan Preston
leaf
python for a decade
leaf
developer on twisted
leaf
now works on eventlet
hide
What
leaf
Actor based systems use actors
leaf
treats "actors" as the computational model
leaf
circular definitions
leaf
form of concurrency
hide
constraints
hide
An actor is a process
leaf
protected memory
leaf
thread of control
hide
Actors can change their own state
leaf
*only* an actor can change their own state
leaf
Actors can create another actor and get it's address
leaf
addresses provide messaging, but can't get access to internals
leaf
no shared state
leaf
actors can only send messages (async) to another address it knows
hide
actors can wait for a specific (kind of) message to arrive in its mailbox
leaf
you don't get responses
leaf
push a message, then wait for a response message
hide
Why
hide
Isolation
leaf
since only Actors have access to their own memory... other actors can't manipulate the internal state of another actor
hide
Simple Control Flow
leaf
each actor's control flow is independent
leaf
code can be written straight line or with simple loops
leaf
threading issues around shared resources not as critical since no shared resource
hide
Message Passing
leaf
Easy to distribute
leaf
across cores
leaf
across UNIX process boundaries
leaf
across machines
hide
Simplified Error Handling
leaf
most exceptional conditions occur while waiting for a message
leaf
timeouts
leaf
network errors
leaf
makes it easier to build fault tolerant systems
hide
How are Actors Implemented
hide
Existing Actor systems
hide
Erlang
leaf
functional
leaf
http://erlang.org/
hide
IO
leaf
http://www.iolanguage.com/
hide
Python
hide
Parley
leaf
http://osl.cs.uiuc.edu/parley
hide
Dramatis
leaf
pypi.python.org/pypi/dramatis
hide
Candygram
leaf
candygram.sf.net
hide
and the author's....
leaf
bitbucket.org/fzzzy/python-actors
leaf
just a prototype
hide
Actor type semantics to python
hide
python-actors
hide
Green Threads for "Processes"
hide
Using eventlet
hide
uses greenlet
leaf
port of stackless as a C Extension
hide
JSON for message serialization
leaf
used to copy messages between in-process actors
leaf
passing real objects would have shared the data structures
leaf
WSGI/HTTP for network protocol
hide
green threads
hide
using OS processes or posix threads:
hide
memory usage grows crazy with lots of them
leaf
few hundred processes
leaf
1000 threads
leaf
time to start the processes/threads non-trivial startup time
hide
Spawning an Actor
hide
every Actor has it's own 'main(self, what)'
leaf
class Hello(actor.Actor):
def main(self, what):
print "Hello, ", what

actor1 = Hello.main("Pycon")
actor2 = Hello.main("World")
hide
Sending a message
leaf
class Send

def main(self, address):
address.cast("Hello")

class Receive
def main(self)
pattern, message = self.receive()


receiver = Receive.spawn() # returns an address
sender = Send.spawn(receiver)
hide
Pattern matching
leaf
actor can wait for a specific message to arrive in it's mailbox
leaf
in erlang: "selective receive"
leaf
python doesn't really have this
hide
his implimentation 'shaped'
leaf
{'hello': str}
leaf
[str]
leaf
(int, str, float)
leaf
address.cast("This does not match")
address.cast("{u'hello': foo}")
hide
network protocol REST interface
leaf
PUT spawns an actor
leaf
redirects to an address
leaf
POST <Address> sends a message
hide
Problem: Modules can contain global state
hide
possibility:
leaf
unique copy of sys.modules for every actor
leaf
seal modules in wrapper objects to prevent modification
hide
reality:
leaf
don't use module global state
hide
Tools for Python Metaprogramming
leaf
writing of programs that write other programs or modifies themselves
leaf
understand and modifiy it's own internal representation, structure,
hide
exec() / eval()
hide
safely execute code in an exec via isolation
leaf
but builtins are still available
leaf
but python is then somewhat unusuable
leaf
inspect.getsource() to get the source code for a function, do string substitution for the code, then exec the code.
hide
Python's Data Model
hide
Magic Methods
hide
ability of override certain operators
leaf
= + - / %
leaf
. [] ()
hide
callable emulation
leaf
__call__(self, ...)
leaf
argument handling
leaf
first class functions
hide
decorators
leaf
a callable that eventually consumes a functions and generally returns another function (typically varient of the passed arg)
hide
decorator patterns
hide
work around the function
leaf
do something; call the function ; do something else
leaf
measure_time
leaf
modify the original functions's output
leaf
from functools import wraps
leaf
decorators with parameters
hide
Class based decorators
leaf
@decorator
def func():
...

func = decorator(func)
hide
class based
leaf
__init__ takes a function
leaf
__call__ runs the function
leaf
class decorators not covered
hide
types
hide
Function type signature
leaf
(code, globals[, name[, argdefs[, )
hide
metaclasses
hide
classes are created
leaf
type(name of class, bases, namespaces)
leaf
__new__(class, ...) -> new class
leaf
__init__(instance, ...) -> new instance
hide
Metaclass patterns
hide
registrations
leaf
e.g. keep track of classes of a particular subclass in a registry
leaf
declarative syntax
leaf
apply decorators to all methods
hide
Import Hooks
leaf
PEP 302
hide
Other tools
hide
Pure python functional programming (pfpp)
leaf
AST hacks
leaf
concurrency optimizations
leaf
Abstract Syntax Tree hacks
hide
Byteplay
leaf
bytecode hacks
hide
Splarnektity
leaf
haskell like pattern matching
leaf
Python Decorator Library
hideflag
MetaPython
leaf
check this one out
hide
macros in python
leaf
lisplike
hide
patmatch
leaf
erlang-style pattern matching
leaf
WebImporter
hide
Python's Dusty Corners
hide
Jack Diederich
leaf
jackdied@gmail.com
leaf
jackdied.blogspot.com
hide
aims not to surprise
leaf
object protocols to make similar things look the same
hide
double-underscore methods
leaf
comparisions
leaf
attr lookup
leaf
iterators
hide
comparision protocols
hide
1 < 'one'
leaf
refuses to guess
leaf
py2 used to use obj identity
leaf
1 == 'one'
leaf
all classes new style
leaf
py
leaf
subclasses of same object sets uses right hand side for equality
leaf
a == b, then b === a
leaf
at first, ask subclass... if definitive, then use it... if not, ask the more base class
hide
attribute protocols
hide
ob.foo
leaf
ob.__dict__ has a key "foo"
leaf
ob's class has an attribute 'foo'
hide
but rarely...
hide
ob's class defines __getattr__
leaf
couldn't find a name, ask me
hide
defines __getattribute__
leaf
ask me about name, always
leaf
a property for foo
hide
descriptors
leaf
determine whether an function object is retrieved as a function or a bound method to an object
leaf
__get__
leaf
staticmethod()
leaf
classmethod()
hide
iterators and iterables
hide
iterables
leaf
return an iterator from __iter__
hide
iterators
leaf
return the next value from __next__()
hide
Context managers
leaf
aquisition/release
leaf
__init__(self)
leaf
__enter__(self):
leaf
__exit__(self):
hide
contextlib for making generator functions into context managers
leaf
def with_lock():
lock = aquire_lock()
try:
yield None:
finally:
lock.release()
hide
pony-build
leaf
only caught the last 10 minutes or so, after Dusty Corners finished
leaf
file and meta data
leaf
pub-sub
hide
but it also sucks
leaf
centralized coordination and sync is not natural to the pony build model
leaf
timeout
leaf
decoupling things complicated for inexperienced "users"
leaf
good authentication model needs to be developed
leaf
thousand ponies whinny
leaf
e.t. phone home
leaf
90% of python software has some semi custom build or test step
leaf
leaderboard
leaf
failed the undergrad test
hide
Seatle: Open P2P Computing
leaf
Justin Cappos
hide
Cloud Computing
leaf
next big thing
leaf
20% of business by 2012
hide
silver lining
leaf
over provisioned
leaf
scale by demand
leaf
no hw purchase
leaf
minimizes IT overhead
hide
dark cloud
leaf
resource cost money
leaf
loss of privacy
leaf
vendor api lockin
leaf
censorship
leaf
Cloud computing erodes software freedom
hide
Peer to peer alternative
leaf
p2p leverages end user computation
leaf
avoid lock in through open protocols
leaf
free
leaf
scalability
hide
challenges
hide
heterogeneity
leaf
lots of differences
leaf
many apps have short use patterns
leaf
fault tolerance
leaf
distributed state management
hide
Seatlle: Making P2P easier
hide
heterogeneity
leaf
provide a portable / virtualized programming abstraction
hide
short use patterns
leaf
always on
hide
like a potluck
leaf
you contribute some resources
leaf
you consume some of what others provide
leaf
others consume what you provide
leaf
or you can have a private potluck
hide
contributed resources
leaf
remotely accessible
leaf
requested through a sharing site
hide
Seattle's Vessel
leaf
portable / interoperable
hide
performance isolated
leaf
cpu
leaf
memory
leaf
disk
leaf
network
leaf
etc
hide
safe
leaf
isolated directory, can do no harm
hide
missing some built-ins, __slots__,
leaf
replacements for import
hide
executing python code safely
hide
phil ????'s safe module
hide
build a parse tree
leaf
AST
leaf
reject things that include things like 'import'
hide
builtins.
leaf
remove some builtins
leaf
provide some default builtins
leaf
and stub out to others
leaf
namespace isolation
hide
provides some libs as alternatives to 'risky ones'
leaf
httpretrieve
leaf
textops
hide
seattlegeni
leaf
sharing resources
hide
potential apps
leaf
file backup
leaf
seatlle.cs.washington.edu
hide
Saturday Afternoon Lightening talks
hide
GvR Python Community service award
leaf
Ken Whitesell
hide
Scrape
leaf
ping
leaf
Unit tests help find what broke
leaf
system tests check that it all works together
leaf
manual system checks take time
leaf
s.go('http://localhost/todo>')
returns region doc

s.doc

print.s.doc.content

s.doc.first('h1')
s.follow('to-do list')
leaf
follow links
leaf
submit forms
leaf
manage cookies (logins)
leaf
find tags by content (exact or regex)
leaf
find tags
leaf
zesty.ca/scrape
hide
Python Debugging Techniques
leaf
code.interact()
hide
pdb
leaf
import pdb; pdb.set_trace()
leaf
logging
leaf
IPython
hide
winpdb
leaf
http://winpdb.org/
leaf
pydev
hide
Geo Tagging in Python / Phatch
leaf
gps data into EXIF header pics
leaf
Phatch creates python 'magic' for end users
leaf
Phaatch = Photo Manipulation Program
leaf
geotag -> text -> save -> plop
leaf
clanmills.com
leaf
phatch.org
hide
Big Brothers Design Rules
hide
Security
leaf
treating all inputs as an attack
hide
Object Design
leaf
Good interface doesn't let bad input break it
hide
Freedom is Slavery
leaf
minimize attack surface
leaf
"There is only one mode and it should be 'secure'"
leaf
principal of Least authority
leaf
code can't affect objects it doesn't know about
leaf
Allen Short
hide
PyCon Swag
leaf
David Goodger
hide
Got Swag
leaf
send shirt design ideas to David or pycon-organizers
hide
Python in tiny embedded systems
hide
for smart grid and beyond
leaf
synapse
leaf
energy
leaf
asset tracking
leaf
security
hide
python for deeply embedded systems
leaf
SNAPpy: A tiny Python VM
leaf
Hardware cost < $3
leaf
runs for *years* on AA
leaf
Uses just 8K flash 2K ram
leaf
hide
PyCharm
leaf
New IDE for python and Django
leaf
refactorings
leaf
Debugger
leaf
unit test runner
leaf
editor
leaf
Version control integration
hide
Web Dev support
leaf
HTML, XML, CSS, Javascript
leaf
plugin for vim emulation
leaf
IntelliJ IDEA
hide
Django Support
leaf
Create new projects
leaf
manage tasks
leaf
jetbrains.com/pycharm
leaf
blogs.jetbrains.com/pycharm
leaf
@pycharm
hide
PEP 385: hg conversion
hide
Dirkjan Ochtman, hg crew
leaf
@djco
hide
hgsubversion bug
leaf
tag edititing
hide
EOL issues
leaf
new extension for mercurial
leaf
need to think more about branches
hide
Python - Hell Yeah
leaf
Jesse Noller
hide
Nasuni
leaf
18 people now
leaf
6 core engineers, 1 of which is a founder
leaf
everyone codes, even the manager
leaf
build. fast
leaf
what?
hide
Virtual NAS device
leaf
fully security
leaf
full versioning
leaf
could stand in front of cloud storage
leaf
hide
python
leaf
tests
leaf
prototypes
leaf
user interface
hide
reqirements
leaf
broad eco system
leaf
ramp up, ramp down
leaf
Duct Tape
leaf
8 months
leaf
fault tolerant virtual hard drive in 8 months
hide
Open Spaces
hide
Testing in Python BoF
hide
Mat harrison
leaf
context sensitive code parser
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puts bars next to his editor when coverage runs
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code parser, editor independent
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can be integrated within editors
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Load Test Your Web Server
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Travis Bear
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The Grinder
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What is load testing
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build a model of a user interaction
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replay that model
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lots of simultaneous sessions
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Max capacity of server
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identityfy stability under load
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correctness
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Grinder
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open source load testing framework written in Java
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Distributed load generation
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many (30+) load generator machines controllable by single Grinder UI
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handles the the threading
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User simulations scripted in Jython
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Why the Grinder
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python friendly
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Java friendly
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10 yr
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Grinder Scripts
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TestRunner class
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__call__() called once per iterations
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Grinder Analyzer
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post process grinder logs to visualize test results
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grinder.sf.net
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Crisscross
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Doug.Hellman@gmail.con
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Racemi, Inc
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DynaCenter
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OEM server image management
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image mobility
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allows cloud building
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N supported OSes
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M supported HW platforms
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captured provision reporting
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only reporting pass/fail, no trending
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needed
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infrastructure changes
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automate image installation
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captured follwed by validation
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reporting
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coverage
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os/hw combinations
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trends
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details
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time series graphs with Flot! (nice looking!)
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Gary Bernhardt
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@garybernhardt
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extracheese.org
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Unit Test
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not what you thing
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One and only one class
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isolation
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Ran 36 tests in 6.234s
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not unit tests
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173 times slower
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from expecter import expect
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Why
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Fast feedback
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Failure localization
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infinite testability
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How
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Test driven dev
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should be
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test driven design
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abstraction
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solid principles
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app-engine
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django-nonrel
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app-engine
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allbuttonspressed.com
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asynctools
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async calls to app engine
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gaebar
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:-)
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google app engine backup and restore
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google apps
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Sunday Morning Lightening talks
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damn... overslept and missed morning lightening talks.
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molly m.ox.ac.uk
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Eventlet
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Async I/O with a Sync Interface
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network services
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process
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too heavyweight
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threads
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non-deterministic
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non-blocking IO
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generally requires callback-style programming
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rules out many existing libs
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The C10K problem
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www.kegel.com/c10k.html
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CoRoutines
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