展平一个非常嵌套的循环[重复]

使用itertools库非常容易。

for x, y, z in itertools.product(a, b, c):    print x, y, z

如何

itertools.product

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)

例：

In [1]: a = range(2)    In [2]: b = range(2, 4)In [3]: c = range(4, 6)In [4]: import itertoolsIn [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: 4x: 0, y: 2, z: 5x: 0, y: 3, z: 4x: 0, y: 3, z: 5x: 1, y: 2, z: 4x: 1, y: 2, z: 5x: 1, y: 3, z: 4x: 1, y: 3, z: 5