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一、函数：
创建函数：使用def语句
举例：定义一个返回斐波那楔数列列表的函数
def fibs(num): result = [0,1] for i in range(num-2): result.append(result[-2]+result[-1]) print(result) fibs(10)
>>>
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
>>>
文档化函数：对函数进行说明，写在函数开头的字符串，它会作为函数的一部分进行存储，称为文档字符串。
举例：给square()函数进行注释
def square(x): ‘‘‘calculates the square of the nmber x‘‘‘ return x*x
#使用此方法访问： >>> square.__doc__ ‘calculates the square of the nmber x‘ >>>
return语句：函数的返回值，起到结束函数的作用，不需要返回时，返回为None
举例：
def test(): print(‘pass‘) return print(‘nothing‘) x = test() print(x) >>> pass None >>>
参数：
形参：函数名后面的变量通常叫做函数的形参；
实参：调用函数时提供的值称为实参；
说明：在函数内为参数赋值新值不会改变外部任何变量的值；
举例：
#不可变参数：字符串、数字和元组 def change(n): n = ‘zyj‘ print(n) name = ‘sl‘ change(name) print(name) >>> zyj sl >>> #可变参数如列表 def change(n): n[0] = ‘zyj‘ print(n[0]) name = [‘sl‘,‘xm‘] change(name) print(name) >>> zyj [‘zyj‘, ‘xm‘] >>> # 保留原始变量的办法： def change(n): n[0] = ‘zyj‘ print(n[0]) name = [‘sl‘,‘xm‘] change(name[:]) print(name) zyj [‘sl‘, ‘xm‘] >>>
使用函数改变数据结构的实现举例
要求：编写一个存储名字，并且能根据条件查找对应的名字
实现：定义数据结构类型为字典，通过键值（first，second）查找对应的name。
def init(data): ‘‘‘初始化数据结构的函数‘‘‘ data[‘first‘] = {} data[‘second‘] = {} def lookup(data,lable,name): ‘‘‘查找人名相同函数‘‘‘ return data[lable].get(name) def store(data,full_name): ‘‘‘将输入名字存储在数据库中函数‘‘‘ names = full_name.split() if len(names) == 1: names.insert(1, ‘‘) labels = ‘first‘,‘second‘ for label,name in zip(labels,names): peole = lookup(data,label,name) if peole: peole.append(full_name) else: data[label][name]=[full_name] >>> storage = {} >>> init(storage) >>> storage {‘first‘: {}, ‘second‘: {}} >>> store(storage, ‘zhao yujiao‘) >>> lookup(storage,‘second‘,‘yujiao‘) [‘zhao yujiao‘] >>> store(storage, ‘zhao qiaojiao‘) >>> lookup(storage,‘second‘,‘yujiao‘) [‘zhao yujiao‘] >>> storage {‘first‘: {‘zhao‘: [‘zhao yujiao‘, ‘zhao qiaojiao‘]}, ‘second‘: {‘yujiao‘: [‘zhao yujiao‘], ‘qiaojiao‘: [‘zhao qiaojiao‘]}} >>> lookup(storage,‘first‘,‘yujiao‘) >>> lookup(storage,‘first‘,‘zhao‘) [‘zhao yujiao‘, ‘zhao qiaojiao‘] >>> store(storage, ‘song qiaojiao‘) >>> storage {‘first‘: {‘zhao‘: [‘zhao yujiao‘, ‘zhao qiaojiao‘], ‘song‘: [‘song qiaojiao‘]}, ‘second‘: {‘yujiao‘: [‘zhao yujiao‘], ‘qiaojiao‘: [‘zhao qiaojiao‘, ‘song qiaojiao‘]}} >>> lookup(storage,‘second‘,‘qiaojiao‘) [‘zhao qiaojiao‘, ‘song qiaojiao‘] >>> store(storage, ‘qiaojiao‘) >>> storage {‘first‘: {‘zhao‘: [‘zhao yujiao‘, ‘zhao qiaojiao‘], ‘qiaojiao‘: [‘qiaojiao‘], ‘song‘: [‘song qiaojiao‘]}, ‘second‘: {‘‘: [‘qiaojiao‘], ‘yujiao‘: [‘zhao yujiao‘], ‘qiaojiao‘: [‘zhao qiaojiao‘, ‘song qiaojiao‘]}}
关键字参数：可以明确每个参数的作用，不需要在乎参数的位置。
def hello_1(greeting,name): print("%s,%s!" % (greeting,name)) def hello_2(name,greeting): print("%s,%s!" % (name,greeting)) hello_1("Hello","World") hello_1(greeting="Hello",name="World") >>> Hello,World! Hello,World! >>>
关键字参数可以在函数中给参数提供默认值，此时调用的时候可以不用提供参数，提供一些或提供所有参数
def hello_3(greeting="Hello",name="World"): print("%s,%s!" % (greeting,name)) hello_3() hello_3("greetings") hello_3("greetings",‘zyj‘) hello_3(name=‘zyj‘) >>> Hello,World! greetings,World! greetings,zyj! Hello,zyj! >>>
位置参数和关键字参数结合使用
def hello_3(name,greeting="Hello",p=‘!‘): print("%s,%s%s" % (greeting,name,p)) hello_3("zyj") hello_3("zyj",p=‘!!!‘) hello_3(name=‘zyj‘) >>> Hello,zyj! Hello,zyj!!! Hello,zyj! >>>
收集参数：参数前加星号将所有值放置在同一个元组中。一个参数里面传递多个值。
def print_params(*params): print(params) print_params(‘zyj‘) print_params(1,2,3) print_params([1],[2],[3]) print_params((1,2),(2,3)) def print_params(title,*params): print(title) print(params) print_params(‘name:‘,‘zyj‘,‘sl‘,‘sb‘) print_params(‘name:‘) >>> (‘zyj‘,) (1, 2, 3) ([1], [2], [3]) ((1, 2), (2, 3)) name: (‘zyj‘, ‘sl‘, ‘sb‘) name: () >>>
收集关键字参数：使用**，返回的是字典
def print_params(**params): print(params) print_params(x=1,y=2,z=3) print_params(x=[1],y=[2],z=[3]) print_params(x=(1,2),y=(2,3)) def print_params(x,y,z=9,*params,**key): print(x,y,z) print(params) print(key) print_params(1,2,3,4,5,6,foo=1,bar=2) print_params(1,2) >>> {‘x‘: 1, ‘y‘: 2, ‘z‘: 3} {‘x‘: [1], ‘y‘: [2], ‘z‘: [3]} {‘x‘: (1, 2), ‘y‘: (2, 3)} 1 2 3 (4, 5, 6) {‘foo‘: 1, ‘bar‘: 2} 1 2 9 () {} >>>
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原文地址：http://www.cnblogs.com/zhaoyujiao/p/5252056.html
