How to use itertools to compute all combinations with repeating elements?
Question: I have tried to use
[itertools](https://docs.python.org/2/library/itertools.html) to compute all
combinations of a list `['a', 'b', 'c']` using `combinations_with_replacement`
with repeating elements. The problem is in the fact that the indices seem to
be used to distinguish the elements:

> Return r length subsequences of elements from the input iterable allowing
> individual elements to be repeated more than once.
>
> Combinations are emitted in lexicographic sort order. So, if the input
> iterable is sorted, the combination tuples will be produced in sorted order.
>
> Elements are treated as unique based on their position, not on their value.
> So if the input elements are unique, the generated combinations will also be
> unique.

Sot this code snippet:

    
    
    import itertools
    
    for item in itertools.combinations_with_replacement(['a','b','c'], 3): 
        print (item)
    

results in this output:

    
    
    ('a', 'a', 'a')
    ('a', 'a', 'b')
    ('a', 'a', 'c')
    ('a', 'b', 'b')
    ('a', 'b', 'c')
    ('a', 'c', 'c')
    ('b', 'b', 'b')
    ('b', 'b', 'c')
    ('b', 'c', 'c')
    ('c', 'c', 'c')
    

And what I need is the combination set to contain elements like: `('a', 'b',
'a')` which seem to be missing. How to compute the complete combination set?


Answer: It sounds like you want
[`itertools.product`](https://docs.python.org/2/library/itertools.html#itertools.product):

    
    
    >>> from itertools import product
    >>> for item in product(['a', 'b', 'c'], repeat=3):
    ...     print item
    ...
    ('a', 'a', 'a')
    ('a', 'a', 'b')
    ('a', 'a', 'c')
    ('a', 'b', 'a')
    ('a', 'b', 'b')
    ('a', 'b', 'c')
    ('a', 'c', 'a')
    ('a', 'c', 'b')
    ('a', 'c', 'c')
    ('b', 'a', 'a')
    ('b', 'a', 'b')
    ('b', 'a', 'c')
    ('b', 'b', 'a')
    ('b', 'b', 'b')
    ('b', 'b', 'c')
    ('b', 'c', 'a')
    ('b', 'c', 'b')
    ('b', 'c', 'c')
    ('c', 'a', 'a')
    ('c', 'a', 'b')
    ('c', 'a', 'c')
    ('c', 'b', 'a')
    ('c', 'b', 'b')
    ('c', 'b', 'c')
    ('c', 'c', 'a')
    ('c', 'c', 'b')
    ('c', 'c', 'c')
    >>>
    

