在 python 中查找(并保留)子列表的重复项

I have a list of lists (sublist) that contains numbers and I only want to keep those exists in all (sub)lists.

例子:

x = [ [1, 2, 3, 4], [3, 4, 6, 7], [2, 3, 4, 6, 7]]

output => [3, 4]

我该怎么做?

解决方案

common = set(x[0])
for l in x[1:]:
    common &= set(l)
print list(common)

或:

import operator
print reduce(operator.iand, map(set, x))