Modern Python Standard Library Cookbook

How to do it...

The Cartesian product is usually what people think of when talking about combinations and permutations.

1. Given a set of elements, A, B, and C, we want to extract all possible couples of two elements, AA, AB, AC, and so on:

>>> import itertools
>>> c = itertools.product(('A', 'B', 'C'), repeat=2)
>>> list(c)
[('A', 'A'), ('A', 'B'), ('A', 'C'),
 ('B', 'A'), ('B', 'B'), ('B', 'C'), 
 ('C', 'A'), ('C', 'B'), ('C', 'C')]

2. In case you want to omit the duplicated entries (AA, BB, CC), you can just use permutations:

>>> c = itertools.permutations(('A', 'B', 'C'), 2)
>>> list(c)
[('A', 'B'), ('A', 'C'), 
 ('B', 'A'), ('B', 'C'), 
 ('C', 'A'), ('C', 'B')]

3. You might even want to ensure that the same couple doesn't happen twice (such as ...