itertools.product

This function lets you iterate over the Cartesian product of a list of iterables.

For example,

for x, y in itertools.product(xrange(10), xrange(10)):
    print x, y

is equivalent to

for x in xrange(10):
    for y in xrange(10):
        print x, y

Like all python functions that accept a variable number of arguments, we can pass a list to itertools.product for unpacking, with the * operator.

Thus,

its = [xrange(10)] * 2
for x,y in itertools.product(*its):
    print x, y

produces the same results as both of the previous examples.

>>> from itertools import product
>>> a=[1,2,3,4]
>>> b=['a','b','c']
>>> product(a,b)
<itertools.product object at 0x0000000002712F78>
>>> for i in product(a,b):
...     print i
...
(1, 'a')
(1, 'b')
(1, 'c')
(2, 'a')
(2, 'b')
(2, 'c')
(3, 'a')
(3, 'b')
(3, 'c')
(4, 'a')
(4, 'b')
(4, 'c')