python中用dict存储function

Python中是没有switch的, 所以有时我们需要用switch的用法, 就只能通过if else来实现了. 但if else写起来比较冗长,这时就可以使用Python中的dict来实现, 比switch还要简洁. 用法如下:

如果是key1的情况就执行func1, 如果是key2的情况就执行func2...(func1, func2...所有的函数的参数形式需要相同),
假设各个函数参数均为(arg1, arg2):
dictName = {"key1":func1, "key2":func2, "key3":func3"...}　　
字典的值直接是函数的名字,不能加引号dictName[key](arg1, arg2)

示例代码如下:

#!/usr/bin/python
import re

def add(x, y): 
    return x + y

def sub(x, y): 
    return x - y

def mul(x, y): 
    return x * y

def div(x, y): 
    return x / y

def main():
    inStr = raw_input("Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.\n")
    inList = re.split("(\W+)", inStr)
    inList[1] = inList[1].strip() 
    print("--------") 
    print(inList) 
    print("--------") 

#Method 1:
    if inList[1] == "+": 
        print(add(int(inList[0]), int(inList[2]))) 
    elif inList[1] == "-": 
        print(sub(int(inList[0]), int(inList[2]))) 
    elif inList[1] == "*": 
        print(mul(int(inList[0]), int(inList[2]))) 
    elif inList[1] == "/": 
        print(div(int(inList[0]), int(inList[2]))) 
    else: pass

#Method 2:
    try:
        operator = {"+":add, "-":sub, "*":mul, "/":div} 
        print(operator[inList[1]](int(inList[0]), int(inList[2]))) 
    except KeyError: 
        passif __name__ == '__main__':


main()


Output:
PS J:\> python .\switchDict.py
Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.1 + 2
-------------------------['1', '+', '2']-------------------------
3
3PS J:\> python .\switchDict.py
Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.4 - 9
-------------------------['4', '-', '9']-------------------------
-5
-5PS J:\> python .\switchDict.py
Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.6 / 5
-------------------------['6', '/', '5']-------------------------
1
1PS J:\> python .\switchDict.py
Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.1 9 9
-------------------------['1', '', '9', ' ', '9']-------------------------PS J:\> python .\switchDict.py
Please input the easy expression:(e.g. 1 + 2.But 1 + 2 + 3 are not accepted.1 ( 9
-------------------------['1', '(', '9']-------------------------PS J:\>

个人感觉, 如果想用switch来解决某个问题, 并且每种情况下的操作在形式上是相同的(如都执行某个函数并且这些函数有相同的参数), 就可以用这种方法来实现.