Python - 函数(function) 的 代码 及 详解

函数(function) 的 代码 及 详解

本文地址: http://blog.csdn.net/caroline_wendy/article/details/17232035

函数(function)的基础知识, 包括参数,返回值, 默认参数(key parameter),关键值(key)参数, 

全局(global)变量,非局部(nonlocal)变量, 可变参数(var args),函数文档(__doc__);

全局(global)变量: 可以修改全局的值;

非局部(nonlocal)变量: 可以在嵌套函数中修改上层函数的值;

关键值(key)参数: 可以通过关键值给函数的形参(parameter)赋值, 可以忽略位置的限定;

可变参数(var args): 可以参数匹配, 赋值给可变参数, 提供多个可变参数;

函数文档(__doc__): 可以输出函数的文档;

代码:

# -*- coding: utf-8 -*-  #==================== #File: abop.py #Author: Wendy #Date: 2013-12-03 #====================  #eclipse pydev, python3.3  #函数 def sayHello():     print('Hello World')      sayHello() sayHello()  #带参数的函数 def printMax(a, b):     if a > b:         print(a, 'is maximum') #python自动生成空格     elif a == b:         print(a, 'is equal to', b)     else:         print(b, 'is maximum')  printMax(3, 4) x = 5 y = 7 printMax(x, y)  #全部变量 num = 50 def func():     global num #全局变量, 不建议使用     print('num is', num)     num = 2     print('Changed local num to', num)      func() print('x is still', num)  #非局部变量 def func_outer():     x = 2     print('x is', x)          def func_inner():         nonlocal x #非局部变量, 函数内可见         x = 5          func_inner()     print('Changed local x to', x)  func_outer()  #默认参数 def say(message, times = 1):     print(message*times)  say('Caroline') say('Wendy', 5)  #关键参数, 指定参数 def func(a, b=5, c=10):     print('a is', a, 'b is', b, 'c is', c)  func(1) #a的值必须要指定 func(2, c=50) func(c = 100, a=5)  #可变参数, *number是数组, **keywords是字典(map) def total(initial=5, *numbers, **keywords):     count = initial     for number in numbers:         count += number     for key in keywords:         print(key) #打印key         count += keywords[key]     return count  print(total(10, 4, 5, 6, Caroline = 50, Wendy = 100))  #返回值, 比较大小使用库函数max def maximum(x, y):     if x>y:         return x     else:         return y  print(maximum(2, 3))  #表面return None def someFunction():     pass  print(someFunction())  #函数文档 #格式: 首行以大写字母开始, 句号结尾, 次行空格, 接下来是描述 def Welcome(x, y):     '''     Welcome to Caroline's world.           Wendy and me will tell you how to write python.     '''     print(x)     print(y)  Welcome('Caroline', 'Wendy') print(Welcome.__doc__)  help(Welcome) #帮助信息

输出:

Hello World Hello World 4 is maximum 7 is maximum num is 50 Changed local num to 2 x is still 2 x is 2 Changed local x to 5 Caroline WendyWendyWendyWendyWendy a is 1 b is 5 c is 10 a is 2 b is 5 c is 50 a is 5 b is 5 c is 100 Wendy Caroline 175 3 None Caroline Wendy      Welcome to Caroline's world.           Wendy and me will tell you how to write python.      Help on function Welcome in module __main__:  Welcome(x, y)     Welcome to Caroline's world.           Wendy and me will tell you how to write python.