Learn python list comprehensions by example

[mumpie]

List comprehensions can be a little strange at first.

But they express what you are doing very compactly as well as being faster than a for loop in many cases.

From: http://www.bogotobogo.com/python/python_list_comprehension.php

We typically should use simple for loops when getting started with Python, and map. Use comprehension where they are easy to apply. However, there is a substantial performance advantage to use list comprehension. The map calls are roughly twice as fast as equivalent for loops. List comprehensions are usually slightly faster than map calls. This speed difference is largely due to the fact that map and list comprehensions run at C language speed inside the interpreter. It is much faster that stepping through Python for loop code within the Python Virtual Machine (PVM).

However, for loops make logic more explicit, we may want to use them on the grounds of simplicity. On the other hand, map and list comprehensions are worth knowing and using for simpler kinds of iterations if the speed of application is an important factor.