python---装饰器用法小结

from django.utils.decorators import method_decorator

def outer(func):
    def inner(*args,**kwargs):               #inner接收参数
        print(args)
        return func(*args,**kwargs)          #将inner得到的参数传给func（），即add（）,形参
    return inner

@outer
def add(b):                                   #接收参数
    a=3
    print(a+b)
add(9)                                        #传参给inner



class aaa():
    @method_decorator(outer)                   #在类中使用装饰器
    def re(self,c):
        print(c+6)

    @outer
    def er(self):
        pass

a=aaa()
a.re(9)

*args,**kwargs的区别

def function(x,y,*args,**kwargs):
    print(type(x))
    print(args)        
    print(kwargs)
    print(type(args))        
    print(type(kwargs))

function(1,2,3,4,5,a=1,b=2,c=3)

<type 'int'>
(3, 4, 5)            　　　　#*args返回的是数组
{'a': 1, 'c': 3, 'b': 2}    #**kwargs返回的字典
<type 'tuple'>
<type 'dict'>

###@wraps：避免被装饰函数自身的信息丢失
----------------------------------
def decorator(func):
    def inner_function():
        pass
    return inner_function

@decorator
def func():
    pass

print(func.__name__)
#inner_function


-----------------------------------
from functools import wraps

def decorator(func):
    @wraps(func) 
    def inner_function():
        pass
    return inner_function

@decorator
def func():
    pass

print(func.__name__)
#func

#类装饰器
----------------
class Decorator(object):
    def __init__(self, f):
        self.f = f
    def __call__(self):
        print("decorator start")
        self.f()
        print("decorator end")

@Decorator
def func():
    print("func")

func()
'''
decorator start
func
decorator end
'''

import time

def decorator(func):
    def wrapper(*args,**kwargs):
        start_time = time.time()
        func(*args,**kwargs)
        end_time = time.time()
        print(end_time - start_time)
    return wrapper

class Method(object):

    @decorator 
    def func(self):
        time.sleep(0.8)

p1 = Method()
p1.func() # 函数调用
'''
0.815999984741
对于类方法来说，都会有一个默认的参数self，它实际表示的是类的一个实例，所以在装饰器的内部函数wrapper也要传入一个参数
- me_instance(任意参数)就表示将类的实例p1传给wrapper，其他的用法都和函数装饰器相同。
'''

#多层装饰器，执行顺序
def X(func):
    print('there is X')                             #1
    def inner():
        print('there is X inner')                   #4
        func()                                      #5---func（）只执行一遍
        print('there is X inner later')             #6
    return inner

def Y(func):
    print('there is Y')                             #2
    def inner():
        print('there is Y inner')                   #3
        func()
        print('there is Y inner later')             #7
    return inner
  
@Y #远
@X #近
def dog():
    print('you are comming')
dog()


---------
there is X
there is Y
there is Y inner
there is X inner
you are comming
there is X inner later
there is Y inner later