Simple cartesian product

[Neel Krishnaswami]

Magnus L. Hetland <mlh at vier.idi.ntnu.no> wrote:
> 
> [Cartesian product using list operators]
>  
> >>> def product(a,b):
> ...     a2 = reduce(lambda l, x, n=len(b): l + [x]*n,
> ...                [[]] + a)
> ...     b = b * len(a)
> ...     return map(None, a2, b)                      

Here's my entry:

def product(a, b):
    u = map(lambda i: a[i/len(a)], range(len(a)*len(b)))
    v = map(lambda j: b[j%len(b)], range(len(a)*len(b))) # Same as b*len(a)
    return map(None, u, v)

>>> product([1,2,3], ['a','b'])
[(1, 'x'), (1, 'y'), (1, 'x'), (2, 'y'), (2, 'x'), (2, 'y')]

Obviously, if you want to save your sanity the nested for-loops are
the way to go. :)


Neel