全排列

def perm(n, begin, end):
    if begin >= end:
        print(n)
    else:
        i = begin
        for num in range(begin, end):
            n[num], n[i] = n[i], n[num]
            perm(n, begin + 1, end)
            n[num], n[i] = n[i], n[num]
n = [1, 2, 3]
perm(n, 0, len(n))

import itertools
print list(itertools.permutations([1, 2, 3, 4],4))  #第二个参数表示，4个数的全排列