Copying nested lists in Python

Question

I want to copy a 2D list, so that if I modify one list, the other is not modified.

For a one-dimensional list, I just do this:

a = [1, 2]
b = a[:]


        

Answer 1

For a more general solution that works regardless of the number of dimensions, use copy.deepcopy():

import copy
b = copy.deepcopy(a)

Answer 2

b = [x[:] for x in a]