Can someone please help me find fault in my code ?
If I create blank 2D matrix with static initial value, it returns correct transposed matrix.
Whereas if I create blank matrix using for loop, it is returning last row for all rows in the answer.

# Original Matrix :
[[1, 2, 3], 
[4, 5, 6], 
[7, 8, 9]]

# Expected Transpose :
[[1, 4, 7],
[2, 5, 8],
[3, 6, 9]]

# Actual Transpose :
[[3, 6, 9],
[3, 6, 9],
[3, 6, 9]]


# Transpose Matrix

def transpose_mtx(original):
    t_cols = len(original)
    t_rows = len(original[0])

    # creating a blank matrix with 0s of transpose shape
    row = [0 for _ in range(t_cols)]
    t_mtx = [row for _ in range(t_rows)]

    # t_mtx = [[0,0,0],[0,0,0], [0,0,0]]
    # if I keep this line instead, it returns correct answer
 
    # rows of original
    for i in range(len(original)):
        # columns of original
        for j in range(len(original[0])):
            # interchange items
            t_mtx[j][i] = original[i][j]
    
    return t_mtx


my_mtx = [[1,2, 3],
          [4, 5, 6],
          [7, 8, 9]]

print(transpose_mtx(my_mtx))