I got back from PyCon last night. I’d taken notes on all the sessions I attended. They’re kind of sketchy, and I don’t know if they’ll be of any use to anyone else, but I figured I’d put them up anyway. My apologies to speakers whom I have crudely paraphrased here. The quality of these notes varies as my energy level waxed and waned.

Michael H Goldwasser Using Python To Teach Object-Oriented Programming in CS1

• Objects later, or objects first?
• Objects first sounds better, but:
  • Students are overwhelmed by Java.
  • People are trying to make Java simpler to teach, but why not just use a different language?
• Python is better:
  • Students can use classes before they create classes
    • stdlib is full of classes: str, list, etc.
  • Interactive interpreter is a great tool for experimentation.
  • Ironically, though you can’t write Java code except in a class, Python primitive types are classes, but Java’s are not.
• Writing classes
  • self is a bit of an obstacle.
    • Code of a method is very consistent.
    • But callers see a different number of parameters, error messages can be confusing.
  • “we’re all adults” access control can be confusing for students.
  • Generics and polymorphism are a strong plus for Python.
• After Python, need to transition to other languages.
  • Don’t have to unteach any Python lessons, unlike other languages.
  • Switch from dynamic to static is easily motivated: static allows the compiler to do lots of work for you.
  • If they can do Python and C++, everything else is in the range in the middle.

Peter Skomoroch, datawrangling.comMPI Cluster Programming with Python and Amazon EC2

• Netflix prize, large dataset.
  • need to do lots of runs, lots of power.
  • How can I get a beowulf cluster?
• Amazon EC2
  • __init__( <machine> ) graphic.
  • Launch instances of machines. Price is $.10 per hour.
  • http://del.icio.us/pskomoroch/ec2
• Parallel programming in Python
  • lots of tools available
• ElasticWulf
• batteries included.
• MPI
  • high performance message passing interface.
  • Standard, point-to-point.
  • flexible but complex.
• examples of pyMPI code.
• I was in over my head here!
  • He kept saying, “This is really easy”
  • I kept hearing, “This is really complicated”

Bruce FrederiksenApplying Expert System Technology to Code Reuse with Pyke

• Pyke grew out of a consulting gig that wanted to reduce code reuse
• What is Code Reuse?
  • Function reuse, but could happen at multiple layers.
  • Current solutions: Adapters, Zope stuff.
  • Limitations: Need to identify functions to call before calling them
    • Dynamic adaptation won’t help.
    • Backward chaining algorithms help here.
• Applying Backward Chaining to Code Reuse: Works great.
• Needed a better explanation of the problem area.
• Pyke is a language for specifying rules with Python code attached.
• Essentially: an inference engine, but the resulting plan from matching rules is Python code to execute.

Kevin Dangoor Rich UI Webapps with TurboGears 2 and Dojo

• Client-side apps in django and Turbogears
• web apps where almost all logic is at the client.
• Dojo templates, Dijit, etc.
• Similar concepts to how server-side web apps work, but moved into Javascript.
• Comet is cool too.
• Summary: Hyper-ajax where as much as possible happens on the browser.

Adrian Holovaty State of Django

• State of Django, Adrian Holovaty
• PyCon has been a nexus of Django activity over the years.
• .96 is latest release, a year old, very conservative.
• trunk == hot_action
• What’s new:
  • Unicode
  • autoescaping
  • Oracle
  • GeoDjango
  • a few sprints.
• Community stuff:
  • Djangosites
  • Djangosnippets
  • Djangogigs
  • Djangopeople.net
  • The Django Book
  • Five other django books
• What’s coming
  • Django is mostly mature
  • queryset refactor
    • model subclassing.
    • 1-1 models
    • finer-grained select_related
  • newforms admin
    • better separation of model and admin
    • hooks for controlling authorization for viewing, changing, etc.
• Announcement: Django Software Foundation formed!

Michael Carter High performance Network IO with Python + Libevent

• Alternatives
  • Twisted
  • asyncore
  • ctypes+libevent
• Quick overview of Network Communication
• Pyevent:
  • Python wrapper over libevent
  • fast: lots happens in C
  • Not much docs

Friday lightning talks

• Noonhat: connect for lunch
• Saturday House: Take your big ideas, make them small, change the world.

Plenary: Twisted announcement: they have a foundation.

Plenary: You *can* Fool All of the People All of the Time Brian Fitz Fitzpatrick

• Three good reasons to lie to your users
• Perception is .9 of the law
• It isn’t lying if you have both sizzle and steak
• Software is additive
• Chinese menu vs zen menu
• Abstractions: leaky
• Keep it simple.
  • Google screen is simple, but is a lie
  • It hides enormous complexity.
  • iPod is a lie: the elegance hides the complexity.
• Don’t be lazy
  • MS Word toolbar craziness: lazy.
  • Larding on options is avoiding decisions.
• Put users first.
  • Listen to what they want.
  • But: they don’t know what they want.
• Speed matters.
  • 1M users * 20 req/day * 500ms * 365 days/yr = 116 years
  • Stop killing your users!
• Google anecdotes:
  • “I didn’t know people worked there!”
  • The whole co going to Disneyland. “But then who’ll do the searches!?”

Plenary Keynote: Intellectual Property and Open Source Van Lindberg. IP and Open Source

• First kill all the lawyers
  • Greatest hits: bad things that came out of IP suits, SCO, RIAA, etc.
  • These days, the most valuable part of a business is its IP.
• Frankly, too much information about the legal aspects of goods, IP, etc.

Mike Bayer SQLAlchemy 0.4 and Beyond

• SQLAlchemy 0.4
  • Lots of developers helping
  • Improved speed
  • simplified code
  • SQL Expression language
    • Smart operators
    • Generic functions
    • Lots of engine-aware differences handled automatically.
  • Collections API: auto-map records to collection classes.
  • “Dynamic” relations:
    • Handle very large manu-to-one relationships.
  • Polymorphic Inheritance
  • Transactional Sessions
    • Including nested transactions where savepoints are supported
    • Two phase commit, for coordinated transactions.
  • Mutable primary keys
  • Can assign SQL expressions to columns for atomic updates.
  • Lots of dialects: Sybase, DB2, Informix
  • Horizontal sharding.
  • Connection event hooks
• Coming up:
  • Migrate

Matt Harrison Managing Complexity (and testing)

• Discussion of code paths, branch coverage, motivations for path analysis
• Continuum of coverage:
  • No testing
  • Line testing
  • Branch testing
  • Structured testing
  • Path testing
• PyMetrics: doesn’t get the metrics quite right.

Brandon Rhodes Using Grok to Walk Like a Duck

• duck typing: cool, but what if your objcet doesn’t quack at all?
• subclassing:
  • Works, but:
  • Creation methods need to take factory arguments.
  • Testing can be difficult: real classes like that may be expensive.
  • May be conflicts between base class methods and the needs of derived
  methods to implement the duck interface.
• mixin: like subclassing, but new methods are in a mixin
  • tests can be easier, b/c you mixin to a new dummy class for testing.
• monkeypatching
  • mentioned only for completeness.
  • Ruby people do this: F
  • “Ruby people are excited b/c their language is prettier than Perl.”
• adapters
  • Give up on the idea of making Messages do something they don’t already do.
  • make a new object using has-a instead of is-a
  • Tests can easily use mock objects.
  • Works great, but wrapping is annoying.
• Adapters work b/c they provide what another piece of code needs.
  • Interfaces are the way to express this need.
• Zope provides interface and adaptation tools
• Grok makes those tools even better.

Jono DiCarlo Case Study of Python Application Development -- Humanized Enso

• build bot
• contractify: program by contract
• Crash exceptions reported back automatically.
• Isn’t Python slow?
  • Profile
  • Take an algorithms course (n00b!)
  • Rewrite critical parts as C extensions.
  • SWIG is cool, SCons is cool.
• Drawing on the screen
  • prototype with wxpython or pygame
  • real thing: pyCairo
• OS interaction
  • win32 extensions.
• Releasing
  • py2exe
  • NSIS

Anna Ravenscroft To RE or not to RE -- Parsing text in Python

• Simple string methods to deal with text.
• Tips and tricks for regular expressions.

Plenary: Making Client-Side Python Suck Less Aza Raskin

• Python on the desktop sucks.
• Big download, silos, ugly
• toolness.com has a prototype of installing Python as a platform ala .net.

Plenary Keynote: Snake Charming the Dragon: the past, present and future of Python and Mozilla Mark Hammond

• Python is the first of the second-class languages
• History, 1998
  • open source was still a curiosity.
  • Netscape released source code to Navigator
  • Then tried to rewrite it from scratch
• Same code used to do the chrome and the meat.
• MS-COM and Corba models adapted as XPCOM, cross-platform, language-independent
• The 1st second-class language:
  • #1 goal is fast stds-compliant browser
  • be the platform for experimenting with new web stds.
• Why the first?
  • first chronologically
  • language features borrowed from python: generators, for ex.
• Hired by ActiveState to build Python XPCOM bindings.
• Python in Mozilla:
  • Python can be used directly
  • <window script-type=”application/x-python”><script src=”...py”/>
  • XULRunner lets you use CSS and XHTML to make native apps.
• pyXPCOM experiences
  • User’s reactions to pyXPCOM
  • Some love it, but perception is no community
• Why no community?
  • Complexity is a barrier to hobbyists.
  • Used by large projects like Mozilla, already busy with their own communities
  • Mozilla and Python each think the other owns it.
• The future of Mozilla
  • 1.8/1.9: mozilla version numbers, not firefox version numbers.
• Mozilla 2.0:
  • Smaller, faster
  • JS 2.0, JIT
• Tamarin virtual machine
  • Created for ActionScript
  • Open-sourced by Adobe
  • JIT, light-weight
  • Trying to fit it in 100K.

Plenary: OLPC Update Ivan Krstić

• Working on power management
• Plugins are the new ifdef
  • Need discipline to make it work
• Deployed laptops in Uruguay and Peru
  • Uruguay: centralized, good tech
  • Peru: dispersed, understand constructionism
• Peru Arahuay pilot
  • Hilltop village in the middle of nowhere
  • What happened when laptops were handed out? Everyone very engaged.

Ian Bicking Consuming HTML

• HTML is democratic, therefore tag soup
• HTML is the most important markup language in the world.
• What to do about bad stuff?
  • Punish, or Guess
• XML’s philosophy is Punish
• Postel’s Law:
  • Be conservative in what you produce, liberal in what you consume.
  • HTML does one half, XML does the other.
• Presentation vs. Semantics
• XHTML: it will never catch on.
• BeautifulSoup
  • Written for screen scraping
  • Forgiving
• html5lib:
  • Reference impl of HTML 5 parsing
  • In theory, *the* correct parsing.
• HTMLParser:
  • Old, rejects lots of HTML, awkward (SAXish)
• lxml:
  • libxml2
  • pretty good parser, similar results to html5lib
  • fast
• minidom: horrible
• lxml: same API as ElementTree, plus a parent pointer, plus lxml.html
• lxml.html: adds methods to Element for HTML.

Jason Pellerin nose: testing for the lazy coder

• Laziness is good:
  • Don’t want to waste your time.
• Write tests first so you never write wasted code.
• How did laziness drive nose
  • Traditional unittest is high-friction
  • py.test is complex
• Demo of writing a simple application with nose tests.
• TDD panic sets in.
  • Remain calm.
  • Write a high-level test that documents and expresses what your project does.
• Nose is easier than unittest
  • Don’t have to write scaffolding to find tests.
• Basics of nose
  • Extends unittest, doesn’t replace it.
  • Simple test definition
  • Automatic test discovery
  • Same output as unittest.
• Writing useful tests
  • Organize tests into modules and packages, with fixtures at every level.
  • Use plain-old assert to test.
  • Use print for debugging.
  • Generate tests from other data.
• Plugins
  • pdb
  • coverage
• Test selection
  • rich methods for subsetting the tests.

Titus Brown Introducing Agile Testing Techniques to the OLPC Project

• Solving social problems technically
• Agile methods include lots of stuff like automated testing.
• Forensic code analysis
  • large sw projects are living organisms
  • We lack tools to study them.
  • CPython has cool hooks
• sys.settrace lets you measure line execution
  • Wouldn’t it be nice to get that from long-running processes.
• OLPC
  • OSS community is intolerant of manual builds
  • They should be intolerant of manual tests
• OLPC GUI has no automated tests
• Testing Death Spiral
  • As features are added, code starts to break.
• Cascade of Attention-Deficit Teenagers
• Continuous Integration
  • sugar-jhbuild pulls 51 packages from the internet!
  • Breaks frequently.
• Simple GUI automation + Live coverage data
• Figserve showing lines of code executed in a running Sugar process.
  • Great for reverse engineering code.
• Conclusions
  • Runtime code tracing is fun
  • GUI automation is not fun