def __isub__(self, mat):
        """ Add a matrix to this matrix.
        This modifies the current matrix """

        # Calls __sub__
        tempmat = self - mat
        self.rows = tempmat.rows[:]     
        return self
 Add a matrix to this matrix.
        This modifies the current matrix 
recipes/Python/578131_A_simple_Matrix_class/recipe-578131.py