Expert Python Programming - Third Edition

Other idioms

Another typical example of a Python idiom is the use of enumerate(). This built-in function provides a convenient way to get an index when a sequence is iterated inside of a loop. Consider the following piece of code as an example of tracking the element index without the enumerate() function:

>>> i = 0
>>> for element in ['one', 'two', 'three']:
...     print(i, element)
...     i += 1
...
0 one
1 two
2 three

This can be replaced with the following code, which is shorter and definitely cleaner:

>>> for i, element in enumerate(['one', 'two', 'three']):
...     print(i, element)
...
0 one
1 two
2 three

If you need to aggregate elements of multiple lists (or any other iterables) in the one-by-one fashion, you can use the built-in zip()