Flipping matrices problem

[Qmohankumar0017]

My question is:
A two dimensional matrix can be represented in Python row-wise, as a list of lists: each inner list represents one row of the matrix. For instance, the matrix

1 2 3
4 5 6
7 8 9
would be represented as [[1, 2, 3], [4, 5, 6], [7, 8, 9]].

A horizonatal flip reflects each row. For instance, if we flip the previous matrix horizontally, we get

3 2 1
6 5 4
9 8 7
which would be represented as [[3, 2, 1], [6, 5, 4], [9, 8, 7]].

A vertical flip reflects each column. For instance, if we flip the previous matrix that has already been flipped horizontally, we get

9 8 7
6 5 4
3 2 1
which would be represented as [[9, 8, 7], [6, 5, 4], [3, 2, 1]].

Write a Python function matrixflip(m,d) that takes as input a two dimensional matrix m and a direction d, where d is either 'h' or 'v'. If d == 'h', the function should return the matrix flipped horizontally. If d == 'v', the function should retun the matrix flipped vertically. For any other value of d, the function should return m unchanged. In all cases, the argument m should remain undisturbed by the function.

So I figured out the solution:

def matrixflip(m,d):
  newm=m[:]
  if d=='v':
    n=len(m)-1
    for i in range(0,len(m)//2):
      newm[i],newm[n-i]=newm[n-i],newm[i]
  elif d=='h':
    n=len(m[0])-1
    for i in range(0,len(m)):
      for j in range(0,len(m)//2):
        newm[i][j],newm[i][n-j]=newm[i][n-j],newm[i][j]
  return newm

The problem is that if I submit my answer, out of the two test cases when it is flipped horizontally i.e d='h' it shows side effect but it works in python interpreter in my laptop without any issues