这就是为什么 Python 的 sum 函数 有一个可选的开始"参数:所以你可以用你添加的那种零对象"来初始化它.在这种情况下，使用零矩阵.

>>>打印(总和(ls，sp.zeros(2)))矩阵([[9, 0], [0, 9]])

My python list contains sympy matrix object, and I need to sum them all. If all list elements are just symbols, then using built-in sum function in python works fine.

import sympy as sp
x = sp.symbols('x')
ls = [x, x+1, x**2]
print(sum(ls))

>>> x**2 + 2*x + 1

But for the elements of matrix type, sum function looks not working.

import sympy as sp
ls = [sp.eye(2), sp.eye(2)*5, sp.eye(2)*3]
print(sum(ls))

>>> TypeError: cannot add <class 'sympy.matrices.dense.MutableDenseMatrix'> and <class 'int'>

How can I resolve this problem?

This is why Python's sum function has an optional "start" argument: so you can initialize it with a "zero object" of the kind you are adding. In this case, with a zero matrix.

>>> print(sum(ls, sp.zeros(2)))
Matrix([[9, 0], [0, 9]])