list of list

Question

I want to create a list of list.

I know i have five rows and four columns

oneRow = [0]*5
ans = [oneRow]*4

print(ans)

ans is a matrix of size 5*4 and all elements are 0 as per my expectation.

ans[1][2] = 2

This above line should change only second row third element as 2 , but it sets third element of all rows as 2. Please suggest

Answer 1

list of list:

ans = [[0]*5 for _ in range(4)]

Answer 2

Ketan Lalcheta if you are wondering why it is necessary to use Bob_Li's solution, then this tutorial will help:
https://nedbatchelder.com/text/names.html

It's an easy article to read, and it explains how Python references work.