[FIXED] Updating 2D array in python

Issue

    size = 10
    table = [[0] * size] * size
    for iter in range(size):
        table[iter][iter] = 9

    for iter in range(size):
        print(table[iter])

I am trying to make all daigonal elements to be 9, but instead it is making all the elements as 9.

Solution

Try using a nested list comprehension to initialize table:

size = 10
table = [[0 for _ in range(size)] for _ in range(size)]
for i in range(size):
    table[i][i] = 9
for row in table:
  print(row)

Output:

[9, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 9, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 9, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 9, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 9, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 9, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 9, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 9, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 9, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 9]

Answered By - Sash Sinha