python函数

>>> def func():
...         print("this is a func()")
...
>>> func()
this is a func()

多个参数：

>>> def add(a,b):
...     print(a+b)
...
>>> add(3,5)
8

默认参数：

>>> def add(a,b=3):
...         print(a+b)
...
>>> add(3,4)
7
>>> add(3)
6

不定长参数：

>>> def func1(*arg):
...         print(arg)
...         print(type(arg))
...
>>> func1(1,'a',5)
(1, 'a', 5)
<class 'tuple'>

>>> def func2(**arg):
...         print(arg)
...         print(type(arg))
...
>>> func2(a=1,b=4,name="xiaofan")
{'b': 4, 'name': 'xiaofan', 'a': 1}
<class 'dict'>

>>> def func2(*arg,**args):
...         print(arg)
...         print(type(arg))
...         print(args)
...         print(type(args))
...
>>> func2('a',1,2,3,x=1,y=10)
('a', 1, 2, 3)
<class 'tuple'>
{'x': 1, 'y': 10}
<class 'dict'>
>>> func2('a',1,2,3)
('a', 1, 2, 3)
<class 'tuple'>
{}
<class 'dict'>
>>> func2(x=1,y=10)
()
<class 'tuple'>
{'x': 1, 'y': 10}
<class 'dict'>

函数返回值：return

>>> def func0():
...         return 1,2
...
>>> func0()
(1, 2)
>>> print(type(func0()))
<class 'tuple'>

>>> def func1(*arg,**args):
...         return arg,args
...
>>>
>>> a,b=func1(1,2,3,x=1,y=2)
>>> a
(1, 2, 3)
>>> b
{'x': 1, 'y': 2}
>>>

显式修改函数返回值：

>>> def func1(*arg,**args):
...          return list(arg),args
...
>>> a,b=func1(1,2,3,x=1,y=2)
>>> a
[1, 2, 3]
>>> b
{'x': 1, 'y': 2}

函数多态：

>>> def add(a,b):
...         print(a+b)
...
>>> add(1,2)
3
>>> add("xaiofan","b")
xaiofanb
>>> add([1,2,3],['x','y','z'])
[1, 2, 3, 'x', 'y', 'z']

函数作用域：

>>> x = 1
>>> def f():
...         x = 10
...         print("it is inside x:",x)
...
>>> f()
it is inside x: 10

global语句的意义是用来在函数内部修改全局变量。

>>> x = 10
>>> def f1():
...         global x
...         x = 100
...         print(x)
...
>>> f1()
100
>>> print(x)
100