Question

Is there a clever way to iterate over two lists in Python (without using list comprehension)?

I mean, something like this:

# (a, b) is the cartesian product between the two lists' elements
for a, b in list1, list2:
   foo(a, b)

instead of:

for a in list1:
    for b in list2:
        foo(a, b)

Answer 1

itertools.product() does exactly this:

for a, b in itertools.product(list1, list2):
  foo(a, b)

It can handle an arbitrary number of iterables, and in that sense is more general than nested for loops.