在python中如何实现列表中元素的所有排列组合？如输入为[✀1✀,✀2✀,✀3✀]和2输出为[✀

#!/usr/bin/python
#Two method for generate a list whose item is all possible permutation and combination come from every item of many list.

A = ['1', '2']
B = ['a', 'b', 'c']
C = ['A', 'B', 'C', 'D']

retList = []
for a in A:
for b in B:
for c in C:
retList.append((a,b,c))
print retList

print '*' * 40

def myfunc(*lists):
#list all possible composition from many list, each item is a tuple.
#Here lists is [list1, list2, list3], return a list of [(item1,item2,item3),...]

#len of result list and result list.
total = reduce(lambda x, y: x * y, map(len, lists))
retList = []

#every item of result list.
for i in range(0, total):
step = total
tempItem = []
for l in lists:
step /= len(l)
tempItem.append(l[i/step % len(l)])
retList.append(tuple(tempItem))

return retList

print myfunc(A,B,C)