在此python函数中返回矩阵结果的正确方法是什么？

Question

这是我的Matrix类的定义

class Matrix(object):

    # Constructor
    def __init__(self, grid):
        self.g = grid
        self.h = len(grid)
        self.w = len(grid[0])

    def inverse(self):
        """
        Calculates the inverse of a 1x1 or 2x2 Matrix.
        """
        if not self.is_square():
            raise(ValueError, "Non-square Matrix does not have an inverse.")
        if self.h > 2:
            raise(NotImplementedError, "inversion not implemented for matrices larger than 2x2.")

        # TODO - your code here

        invert = zeroes(1,1)
        if self.h == 1:
            invert[0][0]=(1/self.g[0][0])

        elif self.h == 2:
            # Calculate the inverse of the square 1x1 or 2x2 matrix.
            a = self.g[0][0]
            b = self.g[0][1]
            c = self.g[1][0]
            d = self.g[1][1]

            factor = 1 / (a * d - b * c)

            invert = [[d, -b],[-c, a]]

            for i in range(self.h):
                for j in range(self.w):
                    invert[i][j] = factor * invert[i][j]  

        return Matrix(invert)

我收到的错误是TypeError：“矩阵”类型的对象没有len（）。但是，结果需要为矩阵大小1x1的倒数。