我正在嘗試使用簡單的遞歸來計算矩陣的行列式（行主序），但是由于某種原因變量matrix在最后一個循環中發生了變化，我不明白為什么，因為我沒有編寫任何更改的代碼變量的值。import mathdef print_m(matrix):  # Print the matrix    for i in range(len(matrix)):        print(matrix[i])def determinant(matrix):# return determinant assuming scanning through first row    if len(matrix[0]) != len(matrix):        print('Not square matrix')        return None    if len(matrix) == 2:        print('LAST STEP EXECUTED')        return matrix[0][0]*matrix[1][1] - matrix[0][1]*matrix[1][0]    def get_reduced_matrix(matrix, column):  #not responsible for changin sign        newM = matrix[1:]        for i in range(len(matrix) - 1):            del newM[i][column]        return newM    output = 0    for i in range(len(matrix)): #value of matrix changed when i turned into 1        print("i =", i)        print_m(matrix)        print('END')        output += matrix[0][i] * determinant(get_reduced_matrix(matrix, i)) * math.pow(-1, i + 1)  # change in sign at last        print('Gonna do the loop again')    return outputmatrix1 = [    [11, 12, 13],    [21, 22, 23],    [31, 32, 33]]print(determinant(matrix1))輸出：C:\Users\jason\Desktop\Python\venv\Scripts\python.exe C:/Users/jason/.PyCharmCE2018.1/config/scratches/sdf.pyi = 0Traceback (most recent call last):  File "C:/Users/jason/.PyCharmCE2018.1/config/scratches/sdf.py", line 38, in <module>[11, 12, 13]    print(determinant(matrix1))[21, 22, 23][31, 32, 33]  File "C:/Users/jason/.PyCharmCE2018.1/config/scratches/sdf.py", line 26, in determinantend    output += matrix[0][i] * determinant(get_reduced_matrix(matrix, i)) * math.pow(-1, i + 1)  # change in sign at lastLAST STEP EXECUTEDTypeError: unsupported operand type(s) for *: 'int' and 'NoneType' #MATRIX LOST SOME OF ITS VALUE HEREgonna do the loop againi = 1[11, 12, 13][22, 23][32, 33]endNot square matrixProcess finished with exit code 1所以矩陣剛剛失去了在第二和第三排的第一列條目，我不知道在所有的事了。就像我說的，我一開始并沒有編寫任何可以更改matrix值的代碼。