Python - Why is result "None"?

Question

A = [1,2]
B = [3,4]
C = A.extend(B)
print(C)

Answer 1

"Extend" method does a work but returns nothing. So C becomes None.

An example:
def func (x,y):
x =x+y
This function returns nothing to it's caller but does a work and changes it's arguments.

Answer 2

Here's a very good explanation about your problem

https://stackoverflow.com/a/29998477

Answer 3

You right! If after print(C) I write print(A), it outputs [1,2,3,4]