jdborg jdborg - 3 months ago 22
Python Question

Python combine two for loops

Currently I would do:

for x in [1,2,3]:
for y in [1,2,3]
print x,y


Is there way of doing something like

for x,y in ([1,2,3],[1,2,3]):
print x,y


Would like to shorten this kind of loop and this throws the "too many to unpack" exception.

Answer

Use itertools.product

import itertools
for x, y in itertools.product([1,2,3], [1,2,3]):
    print x, y

prints all nine pairs:

1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3

UPDATE: If the two variables x and y are to be chosen from one list, you can use the repeat keyword (as proposed by agf):

import itertools
for x, y in itertools.product([1,2,3], repeat=2):
    print x, y