Copies and bindings between python objects

Question

Given a matrix, A of size M x N of 0s and 1s. If an element is 0, set its entire row and column to 0.

Input 1:
    [   [1, 0, 1],
        [1, 1, 1], 
        [1, 1, 1]   ]

Output 1:
    [   [0, 0, 0],
        [1, 0, 1],
        [1, 0, 1]   ]

My Code:

def setZeroes(self, A):
    B=A
    for i in range(len(A)):
        for j in range(len(A[i])):
            if(A[i][j]==0):
                for x in range(len(A[i])):
                    B[i][x]=0
                    for y in range(len(A)):
                        B[y][j]=0
        A=B
    return A

Is creating a zero matrix. What do I miss ?

Answer 1

import copy

def setZeroes(A):
   B=copy.deepcopy(A)
   for i in range(len(A)):
       for j in range(len(A[i])):
           if(A[i][j]==0):
               for x in range(len(A[i])):
                   B[i][x]=0
               for y in range(len(A)):
                   B[y][j]=0
   return B

A =  [   [1, 0, 1],
        [1, 1, 1], 
        [1, 1, 1]   ]

print(setZeroes(A))

since, array is pass by reference, you have to deepcopy it.