why the answer is wrong?!

Question

why in this code, 't' will be changed?

S = [[511 for i in range(3)] for j in range(3)]
t = S.copy()
S[0][2] = 76
print(t)

Answer 1

Because t is just another label that is attached to the same list. Changing S changes t as well. To create an independent list, use deepcopy:

from copy import deepcopy

S = [[511 for i in range(3)] for j in range(3)]
t = deepcopy(S)

Answer 2

What answer are you reffering to?

Please add more informations to your question.

Answer 3

@Anna tell me more about 'list.copy()' and its properties.

Answer 4

@Dragonxiv, I want a backup of my list, but it'll be changed.