此只支持十以内的计算，所以如果需要通用的话还需改进！！！

from Stack import *


def funcations(n):
    po=[]
    stack=Stack()
    for i in range(len(n)):
        po.append(n[i])
    for token in po:
        if token in '0123456789':
            stack.push(int(token))
        else:
            operation_1=stack.pop()
            operation_2=stack.pop()
            result=math(operation_1,operation_2,token)
            stack.push(int(result))
    return stack.get_stack()

def math(op1,op2,token):
    if token=='+':
        return op1+op2
    elif token=='-':
        return op2-op1
    elif token=='*':
        return op1*op2
    else:
        return op2/op1


if __name__ == '__main__':
    n='543*-'
    print(funcations(n))