python_装饰器

装饰器：

def wrapper(func):
    if login('kk'):
        return func
  
def login(user):
    if user == 'kk':
        return True
    else:
        print "invalid username"

def readirct(url):
    pass

@wrapper
def home():
    print "show home page!"


home()

简单装饰器语法：

def wrapper(func):

    def result():     

        print 'before'

        func()

        print 'after'

    return result

 

@wrapper  #语法调用装饰器，把foo函数以参数形式传进wrapper函数里

def foo():

    print 'foo'

foo()

 

结果是：

before
foo
after

 

import functools


def wrapper(func):
    @functools.wraps(func)
    def wrapper():
        print 'before'
        func()
        print 'after'
    return wrapper

@wrapper
def foo():
    print 'foo'

#!/usr/bin/env python
#coding:utf-8
 
def Before(request,kargs):
    print 'before'
     
def After(request,kargs):
    print 'after'
 
 
def Filter(before_func,after_func):
    def outer(main_func):
        def wrapper(request,kargs):
             
            before_result = before_func(request,kargs)
            if(before_result != None):
                return before_result;
             
            main_result = main_func(request,kargs)
            if(main_result != None):
                return main_result;
             
            after_result = after_func(request,kargs)
            if(after_result != None):
                return after_result;
             
        return wrapper
    return outer
     
@Filter(Before, After)
def Index(request,kargs):
    print 'index'
     
     
if __name__ == '__main__':
    Index(1,2)

装饰器传动态参数:

def auth(func):
    def inner(*args,**kwargs):
        print 'before'
        func(*args,**kwargs)
        print 'after'
    return inner

@auth
def a1():
    print 'a1'
@auth
def a2(k):
    print 'a2 + %s' % k
@auth
def a3(r,t):
    print 'a3 +%s+%s' % (r,t)

结果：

before
a1
after
before
a2 + ddd
after
before
a3 +ss+gg
after

 

被装饰函数里有返回值：

def auth(func):
    def inner(*args,**kwargs):
        print 'before'
        temp = func(*args,**kwargs)
        print 'after'
        return temp
    return inner

@auth
def server_list(arg):
    print '%s a' % arg
    s_list = ['a1','a2','a3']
    return s_list

ret = server_list('test')
print ret

结果：

before
test a
after
['a1', 'a2', 'a3']

得到了返回值ret

运用装饰器写的简单用户登陆：

def login():
    name = 'cba'
    if name == 'nba':
        return True
    else:
        return False


def auth(func):
    def inner(*args,**kwargs):
        is_login = login()
        if not is_login:
            return u'非法用户!'
        print 'before'
        temp = func(*args,**kwargs)
        print 'after'
        return temp
    return inner

@auth
def server_list(arg):
    print '%s a' % arg
    s_list = ['a1','a2','a3']
    return s_list

@auth
def a3(r,t):
    print 'a3 +%s+%s' % (r,t)

ret1 = a3('sss','kkk')
print ret1

print '============================================='
ret = server_list('test')
print ret

结果：

非法用户!
=============================================
非法用户!

简单传key或token的登陆验证：

def login(token):
    loca = 'sdjkjisldkasld.,sdijkosdjhjshdjaa%'
    if loca == token:
        return True
    else:
        return False


def auth(func):
    def inner(*args,**kwargs):
        key = kwargs.pop("token")  #这里pop把字典中key为token的值获取，并把该token参数去掉，不会影响下面原生func函数传参错误
        is_login = login(key)
        if not is_login:
            return u'非法用户!'
        print 'before'
        temp = func(*args,**kwargs)
        print 'after'
        return temp
    return inner

@auth
def server_list(arg):
    print '%s a' % arg
    s_list = ['a1','a2','a3']
    return s_list


key = 'sdjkjisldkasld.,sdijkosdjhjshdjaa%'
print '============================================='
ret = server_list('test',token=key)
print ret

结果：

=============================================
before
test a
after
['a1', 'a2', 'a3']

多个装饰器：

def w1(func):
    def inner():
        print 'w1 before'
        func()
        print 'w1 after'
    return inner

def w2(func):
    def inner():
        print 'w2 before'
        func()
        print 'w2 after'
    return inner

@w1
@w2
def foo():
    print 'foo'

foo()

结果：

w1 before
w2 before
foo
w2 after
w1 after  

它的原理相当于，刚开始有个盒子foo，然后外面套上一层w2，再套一层w1，要看foo则需要从外面w1往里一层层拨开，从代码看也是从上往下执行！

装饰器加参数：

#!/usr/bin/env python
#coding:utf-8
  
def Before(request,kargs):
    print 'before'
      
def After(request,kargs):
    print 'after'
  
  
def Filter(before_func,after_func):
    def outer(main_func):
        def wrapper(request,kargs):
              
            before_result = before_func(request,kargs)
            if(before_result != None):
                return before_result;
              
            main_result = main_func(request,kargs)
            if(main_result != None):
                return main_result;
              
            after_result = after_func(request,kargs)
            if(after_result != None):
                return after_result;
              
        return wrapper
    return outer
      
@Filter(Before, After)
def Index(request,kargs):
    print 'index'

Index(11,22)

结果：

before
index
after

 后续。。