Skip to main content

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:


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 ...

Popular posts from this blog

Running your own one person company

Recently there was a post on PuneTech on mom's re-entering the IT work force after a break. Two of the biggest concerns mentioned were : Coping with vast advances (changes) in the IT landscape Balancing work and family responsibilities Since I have been running a one person company for a good amount of time, I suggested that as an option. In this post I will discuss various aspects of running a one person company. Advantages: You have full control of your time. You can choose to spend as much or as little time as you would like. There is also a good chance that you will be able to decide when you want to spend that time. You get to work on something that you enjoy doing. Tremendous work satisfaction. You have the option of working from home. Disadvantages: It can take a little while for the work to get set, so you may not be able to see revenues for some time. It takes a huge amount of discipline to work without a boss, and without deadlines. You will not get the benefits (insuran

Testing Groovy domain classes

If you are trying to test Grails domain class constraints by putting your unit test cases in the 'test/unit' directory, then your tests will fail because the domain objects will not have the 'valdate' method. This can be resolved in two ways: Place the test cases inside test/integration (which will slow things down) Use the method 'mockForConstraintsTests(Trail)' to create mock method in your domain class and continue writing your test cases in 'test/unit' What follows is some example code around this finding. I am working on a Groovy on Grails project for a website to help programmers keep up and refresh their skills. I started with some domain classes and then moved on to write some unit tests. When we create a Grails project using grails create-app , it creates several directories, one of which is a directory called 'test' for holding unit tests. This directory contains two directories, 'unit', and 'integration' for uni

My first impressions of Python for the second time

I had worked a bit in Python many years back. Since then I have forgotten almost everything I learned back then. I think the phrase "Out of sight out of mind" applies perfectly to my mind. Since the last few days, I have started relearning Python, and this time I am recording my impressions of Python after having come to it from a Java background. Indentation: Python uses indentation to specify blocks of code, instead of curly braces. I like this, because we anyways indent code to increase readability, so why not achieve two tasks together. Code looks much cleaner without the curly braces. However there may be a little downside. Everyone in the team will have to set up their IDE's in the same way. Things might fall apart if some people use tabs and others use spaces for indentation. Access modifiers: Python does not have public, private, and protected keywords. Everything is public. However, private members can be specified with a leading single underscore. If we use