Sunday, August 23, 2009

Lack of design patterns in Python

While searching for PyCon videos, I came across Joe Gregorio's very good video on (lack of) design patterns in Python. I have also added the video timeline along with some notes I made for myself and my takeaway. Enjoy the video.




Timeline:
[00:00] - Start
[00:15] - People pick tools based on a mythology and not necessarily facts
[02:35] - Python isn't just Java without the compiler
[03:34] - Design patterns are also a sign of weakness in a language
[04:06] - Lack of design patterns in Python (proof of lack)
[06:10] - Patterns are built into Python
[07:00] - Strategy pattern in Python the wrong and right way
[07:36] - The strategy pattern is invisible in languages with first-class functions
[08:07] - Some other language features in Python (first class functions, metaprogramming, iterators, closures)
[09:17] - The iterator pattern (iterators) is also built into Python
[09:36] - The observer pattern is also built into Python
[10:17] - Factory method pattern in Python (
[10:34] - Abstract Factory Pattern
[10:40] - Strategy pattern goes away becaise of first class functions
[11:08] - Drawing some useful conslusions
[12:20] - Drawing light on Python from the perspective of patterns
[12:31] - Thread Pool and Concurrency patterns (should we be talking about language features in Python for concurrency patterns???)
[13:49] - Channels (a model for concurrent processes)
[15:12] - PyCSP (implmentation of csp on top of Python)
[18:42] - Conclusions, summary, and questions
[19:17] - end (video goes on for a few more seconds waiting for questions)



Notes:
There are very few references to design patterns in Python mailing lists and discussions around Python... design patterns could be a sign of weakness in a language... patterns are built into Python (hence very little discussion)...strategy pattern is invisible in languages with first class functions...



Takeaway:
If you have to implement a design pattern, first look at language features and try to determine if any can be used instead of the pattern or at least assist in the implementation of the pattern while programming in that language.

Ask yourself if a language feature would make that pattern part of the language itself.

Concurrency patterns are a rich area to look at.



References:


3 comments:

Vasudev Ram said...

Hi Parag,

I'm not sure but I think Alex Martelli has one or two presentations on design patterns for Python. Try googling for them using appropriate keywords.

- Vasudev

Vasudev Ram said...

Update: Yes, there are some.

See this google search:

python design patterns

Parag said...

Thanks Vasudev,

I will do a search for Python design patterns ...