Find intersection of two nested lists?

Question

I know how to get an intersection of two flat lists:

b1 = [1,2,3,4,5,9,11,15]

b2 = [4,5,6,7,8]

b3 = [val for val in b1 if val in b2]

or

def intersect(a, b):

return list(set(a) & set(b))

  print intersect(b1, b2)

But when I have to find intersection for nested lists then my problems start:

c1 = [1, 6, 7, 10, 13, 28, 32, 41, 58, 63]

c2 = [[13, 17, 18, 21, 32], [7, 11, 13, 14, 28], [1, 5, 6, 8, 15, 16]]

In the end, I would like to receive:

c3 = [[13,32],[7,13,28],[1,6]]

Can you guys give me a hand with this?

Answer 1

To find the intersection of two nested lists, you need not define intersection. It's already a first-class part of the set.

>>> b1 = [1,2,3,4,5,9,11,15]

>>> b2 = [4,5,6,7,8]

>>> set(b1).intersection(b2)