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 nested 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.
[[x,y,z] for x in [1,2,3] for y in [4,5,6] for z in [7,8,9]] it should scale, no?
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.
