为什么矩阵的所有行都与最后一行相同?

有人能帮我找出代码中的错误吗?如果我创建一个具有静态初始值的空白二维矩阵,它将返回正确的转置矩阵。而如果我使用for循环创建一个空白矩阵,它会返回答案中所有行的最后一行。

# 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))