Python编写一个简单计算器

一个计算器最主要的功能是加减乘除，那么用 Python 可以怎样实现呢

#!/usr/bin/env python

# -*- coding:utf-8 -*-

# @Time    : 2018/1/22 22:29

# @Author  : zhouyuyao

# @File    : daemonCalculator.py

# PyCharm 2017.3.2 (Community Edition)

# Build #PC-173.4127.16, built on December 19, 2017

# JRE: 1.8.0_152-release-1024-b8 amd64

# JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o

# Windows 10 10.0

# Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) 

# [MSC v.1900 64 bit (AMD64)] on win32

def add(string):

    total = 0

    numbers = []

    numbers += string.split("+")

    for num in numbers:

        total += int(num)

    print("{0}={1}".format(string,total))

def reduce(string):

    result = 0

    numbers = []

    numbers += string.split("-")

    result = int(numbers[0])

    numbers.pop(0)

    for num in numbers:

        result -= int(num)

    print("{0}={1}".format(string,result))

def ride(string):   # 乘

    total = 1

    numbers = []

    numbers += string.split("*")

    for num in numbers:

        total *= int(num.strip())

    print("{0}={1}".format(string,total))

def division(string):

    result = 0

    numbers = []

    numbers += string.split("/")

    result = int(numbers[0])

    numbers.pop(0)

    for num in numbers:

        result /= int(num.strip())

    print("{0}={1}".format(string,result))

if __name__ =="__main__":

    print("###############################")

    print("#####欢迎来到计算器工作中心######")

    print("###############################")

    print("1：加法 (a+b+c+d···)")

    print("2：减法 (a-b-c-d···)")

    print("3：乘法 (a*b*c*d···)")

    print("4：除法 (a/b/c/d···)")

    method = input("Please input number(1/2/3/4): ")

    if method == "1":

        string = input("请输入您的表达式：")

        add(string)

    elif method == "2":

        string = input("请输入您的表达式：")

        reduce(string)

    elif method == "3":

        string = input("请输入您的表达式：")

        ride(string)

    elif method == "4":

        string = input("请输入您的表达式：")

        division(string)

    else:

        print("The string you input is error.")