Python：遍历子列表

Question

I have a project where I am trying to edit portions of nested lists. Say I started with this list:

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

I want to iterate over a portion of this list so that I get an output that is a square of ones in the center like so.

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

I tried using a for-loop to iterate through the list and a nested for loop to iterate through the sub-lists. However, that did not work. What I got instead was this list:

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

Here is my code:

list = [[0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0]]

for i in range(1,4):
    for j in range(1,4):
        list[i][j] = 1

Why won't this code work? I have searched for a day or two and have not found an answer. Thank you in advance to whoever takes the time to answer or comment.

Answer 1

The code you posted is working fine:

>>> list = [[0, 0, 0, 0, 0],
...         [0, 0, 0, 0, 0],
...         [0, 0, 0, 0, 0],
...         [0, 0, 0, 0, 0],
...         [0, 0, 0, 0, 0]]
>>> 
>>> for i in range(1,4):
...     for j in range(1,4):
...         list[i][j] = 1
... 
>>> pprint(list)
[[0, 0, 0, 0, 0],
 [0, 1, 1, 1, 0],
 [0, 1, 1, 1, 0],
 [0, 1, 1, 1, 0],
 [0, 0, 0, 0, 0]]

Check that your code actually looks like what you posted here.