Python 装饰器

发布时间：2019-08-13 07:41:24编辑：auto阅读（37）

第1章 装饰器


1.1什么是装饰器？

装饰器就是用来为被装饰对象新增功能的工具/函数

1.2装饰器原则：

1.     不修改被装饰对象的源代码

2.     不修改被装饰对象的调用方式

1.3装饰器的目标：为被装饰对象加上新功能

import time

def index():
    time.sleep(1)
    print('index page')

def outter(func):
    defwrapper():
        start=time.time()
        func()
        stop=time.time()
        print(stop - start)
    returnwrapper
index=outter(index)
index()

第2章 装饰器语法糖：

在被装饰器对象正上方单独一行写：@装饰器的名字

import time

def outter(func):
    defwrapper():
        start=time.time()
        func()
        stop=time.time()
        print(stop - start)
    returnwrapper

@outter #index=outter(index)
def index():
    time.sleep(1)
    print('index page')

index()

2.1 装饰器修订：让装饰器可以装饰有参和无参函数

import time

def outter(func):
    defwrapper(*args,**kwargs):
        start=time.time()
        res=func(*args,**kwargs)
        stop=time.time()
        print(stop - start)

       return res
    returnwrapper

@outter #index=outter(index)
def index():
    time.sleep(1)
    print('index page')

@outter
def home(name):
    time.sleep(1)
    print('home index')

index()
home('jiang')

2.2练习：在通过认证后，才能运行相关功能

import time

def outter(func):
    defwrapper(*args,**kwargs):
        start=time.time()
        func(*args,**kwargs)
        stop=time.time()
        print(stop - start)
    returnwrapper

def auth(func):
    defwrapper(*args, **kwargs):
        name=input('请输入用户名：').strip()
        passwd=input('请输入密码：').strip()
        ifname == 'jiang'and passwd == '123':
            res=func(*args, **kwargs)
            returnres
        else:
            print('认证失败')
    returnwrapper

@auth
@outter #index=outter(index)
def index():
    time.sleep(1)
    print('index page')

@outter
def home(name):
    time.sleep(1)
    print('home index')

index()

第3章 叠加装饰器

加载顺序：自下而上

执行顺序：自上而下

import time

current_user={'username':None}

def timmer(func):
    defwrapper(*args,**kwargs):
        start=time.time()
        res=func(*args,**kwargs)
        stop=time.time()
        print(stop-start)
        returnres
    returnwrapper

def auth(func):
    defwrapper(*args,**kwargs):
        ifcurrent_user['username']:
            res=func(*args,**kwargs)
            returnres
        name=input('username>>: ').strip()
        passwd=input('password>>: ').strip()
        ifname == 'jiang'and passwd == '123':
            current_user['username']=name
            res=func(*args,**kwargs)
            returnres
        print('用户名或者密码错误')
    returnwrapper
@timmer
@auth
def index():
    print('from index')
@auth
def home():
    print('from home')

index()
home()

第4章 有参装饰器：

import time

current_user={'username':None}

def outter(engine):
    defauth(func):
        defwrapper(*args,**kwargs):
            ifcurrent_user['username']:
                res=func(*args,**kwargs)
                return res
            name=input('username>>: ').strip()
            passwd=input('password>>: ').strip()
            ifengine == 'mysql':
                if name == 'jiang'and passwd == '123':
                    current_user['username']=name
                    print('基于mysql的认证')
                    res=func(*args,**kwargs)
                    return res
                else:
                    print('用户名或者密码不正确')
            elifengine == "ldap":
                print('基于ldap 的认证')
            else:
                print('基于文件的认证')
        returnwrapper
    returnauth

@outter(engine='mysql')
def index():
    print('from index')

@outter(engine='ldap')
def home():
    print('from home')

index()
home()

 

第5章 无参装饰器

import time

def timmer(func):

    defwrapper(*args,**kwargs):

        start_time=time.time()

        res=func(*args,**kwargs)

        stop_time=time.time()

        print('run time is %s' %(stop_time-start_time))

        returnres
    
    returnwrapper


@timmer

def foo():
    
    time.sleep(1)
    
    print('from foo')
foo()

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