How to use Python well?

[Steven D'Aprano]

On Wed, 16 Feb 2011 10:35:28 -0800, snorble wrote:

> I use Python a lot, but not well. I usually start by writing a small
> script, no classes or modules. Then I add more content to the loops, and
> repeat. It's a bit of a trial and error learning phase, making sure I'm
> using the third party modules correctly, and so on. I end up with a
> working script, but by the end it looks messy, unorganized, and feels
> hacked together. I feel like in order to reuse it or expand it in the
> future, I need to take what I learned and rewrite it from scratch.
[...]
> Or maybe I'm looking for is best practices for how to organize the
> structure of a Python program. I love Python and I just want to be able
> to use it well.

I don't think best practice for writing Python is that much different 
from best practice for other languages. The main difference is that 
Python is multi-paradigm: you can mix procedural, functional and object-
oriented code in the one program.

You should read about bottom-up and top-down programming. You'll probably 
end up doing some of both, but mostly top-down.

The most important thing is structured programming and modularization. 
The debate over structured programming was won so decisively that people 
have forgotten that there was ever an argument to be made for spaghetti 
code!

You can learn a lot (and lose a lot of time!) reading the c2.com wiki at 
http://c2.com/cgi/wiki. These may be useful:

http://c2.com/cgi/wiki?StructuredProgramming
http://c2.com/cgi/wiki?WhatIsRefactoring


Break your code up into small pieces, whether you use functions or 
classes doesn't really matter, although for small scripts functions are 
simpler and have less mental overhead. Instead of writing one giant 
monolithic block of code that does twenty things, write one function for 
each thing, and then one extra main function to call them. This 
encourages code reuse, ease of testing, and simplifies maintenance.


I find that I've learned more from "things to avoid" than from "things to 
do". Something about reading about disasters makes it really clear why 
you shouldn't do it that way :)

Avoid:

* GOTO, but Python doesn't have that :)

* Copy-and-paste programming. If you want to do almost the same thing 
twice, don't copy the relevant code, paste it, and make a small 
modification to it. Write one or more functions that handle the common 
code, and call the function.

* Functions that do unrelated things. Functions should do one thing, 
although that "thing" can get quite complicated.

* Don't sweep errors under the rug. Don't catch exceptions unless you can 
do something about them. "Just ignore it, I'm sure it's not important" is 
rarely appropriate.


See also: 
http://c2.com/cgi/fullSearch?search=CategoryDevelopmentAntiPattern



-- 
Steven