If I have a set of loops like this:
x = [[...],[...],[...]]
for a in x[0]:
for b in x[1]:
for c in x[2]:
# Do something with a,b,c
Is there a simple way to simplify it, especially if there are more levels to it? It seems like something quite easy to do, but I just can't figure it out.
It's quite easy with the itertools library.
for x, y, z in itertools.product(a, b, c):
print x, y, z
How itertools.product could be implemented:
def product(*args, **kwds):
# product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
# product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
pools = map(tuple, args) * kwds.get('repeat', 1)
result = [[]]
for pool in pools:
result = [x+[y] for x in result for y in pool]
for prod in result:
yield tuple(prod)
Example:
In [1]: a = range(2)
In [2]: b = range(2, 4)
In [3]: c = range(4, 6)
In [4]: import itertools
In [5]: list(itertools.product(a, b, c))
Out[5]:
[(0, 2, 4),
(0, 2, 5),
(0, 3, 4),
(0, 3, 5),
(1, 2, 4),
(1, 2, 5),
(1, 3, 4),
(1, 3, 5)]
In [6]: for x, y, z in itertools.product(a, b, c):
...: print 'x: %d, y: %d, z: %d' % (x, y, z)
...:
x: 0, y: 2, z: 4
x: 0, y: 2, z: 5
x: 0, y: 3, z: 4
x: 0, y: 3, z: 5
x: 1, y: 2, z: 4
x: 1, y: 2, z: 5
x: 1, y: 3, z: 4
x: 1, y: 3, z: 5
