How do I insert a list into another list?

Question

I have two lists:

A = [1,2,3]
B = [4,5,6]

Is there an elegant way to insert B into A at an arbitrary position?

Hypothetical output:

[1,4,5,6,2,3]

Obviously I could iterate through B and insert them one at a time, but I figured there was a better way.

Answer 1

def insert(outer, inner, pos):
  outer[pos:pos] = inner

Answer 2

A[1:1] = B

A will be [1, 4, 5, 6, 2, 3]