Multi dimensional array python bug?

Question

Code:

from array import *
import json

s = [[0]*5]*5

list1 = s

d = json.dumps(s)
list2 = json.loads(d)

list1[0][0] = 1
list2[0][0] = 1

print(list1)

print(list2)

This outputs:

[[1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0]]

[[1, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]

Why does it not output the same? Why does list1 set the entire column to value one rather than only index 0,0 ??? Any explanation, is this a bug or a feature?