Automatically nested for loops in python

I am aware that two collections can be accessed simultaneously using

for i,j in zip([1,2,3],[4,5,6]):
    print i,j

1 4
2 5
3 6

What I would like to do is something like this:

for i,j in [[1,2,3],[4,5,6]]:
    print i,j

1 4
1 5
1 6
2 4
2 5
2 6
3 4
3 5
3 6

I want python to automatically create the ne开发者_如何学JAVAsted for loop for me. I would like to avoid using many nested for loops in my code when the list dimension gets up to 5 or 6. Is this possible?

---

Try

for i, j in itertools.product([1, 2, 3], [4, 5, 6]):
    print i, j

---

>>> [[x,y] for x in [1,2,3] for y in [4,5,6]]
[[1, 4], [1, 5], [1, 6], [2, 4], [2, 5], [2, 6], [3, 4], [3, 5], [3, 6]]

It should be pretty easy to get what you want out of the resulting list.

---

I've had some cases where the logic for what needs to be iterated over is rather complex -- so you can always break that piece out into it's own generator:

def it():
    i = 0
    for r in xrange(rows):
        for c in xrange(cols):
            if i >= len(images):
                return
            yield r, c, images[i], contents[i]
            i += 1

for r, c, image, content in it():
    # do something...

But typically I find just spelling simple nested loops out to be better than obfuscating what you're looping over into a call to some other code. If you have more than 2-3 loops nested, the code probably needs refactoring anyway.