裝飾器需要掌握以下知識點：

1.為被裝飾對象提供新功能的工具

2.裝飾器本身、被裝飾對象可以是任意可調用對象

3.軟件一旦上線後，應該對修改封閉，對擴展開放

4.原則：

• 不修改被裝飾對象的源代碼
• 不修改被裝飾對象的調用方式

#示例代碼1
import time


# 裝飾器
def outter(func):

    def wrapper(*args, **kwargs):
        start_time = time.time()
        res = func(*args, **kwargs)
        end_time 
 
= time.time()
        print(‘run time is %s‘ % (end_time - start_time))
        return res
    return wrapper


# 被裝飾函數
@outter # inner = outter(inner)
def inner():
    print("This is inner.")
    time.sleep(3)


@outter # home = outter(home)
def home(name):
    print(‘welcome %s‘ %name)
    time.sleep(
 
2)
    return 123


inner()
print(‘-----‘)
home(‘cooky‘)

6.示例代碼2：裝飾器模板

#示例代碼2
def outter(func):
    def inner(*args, **kwargs):
        res = func(*args, **kwargs)
        return res
    return inner

7.示例代碼3無參裝飾器：模擬實現用戶驗證

#示例代碼3
import time
current_userinfo = {‘user‘:None}


def outter(func):
    
 
def wrapper(*args, **kwargs):
        if current_userinfo[‘user‘]:
            return func(*args, **kwargs)
        user = input(‘please input your username:‘).strip()
        pwd = input(‘please input your password:‘).strip()
        if (user == ‘cooky‘ and pwd == ‘123‘):
            print(‘login successfully‘)
            current_userinfo[‘user‘] = user
            res = func(*args, **kwargs)
            return res
        else:
            print(‘login failed‘)
    return wrapper


@outter
def inner():
    print("This is inner.")
    time.sleep(3)


@outter
def home(name):
    print(‘welcome %s‘ %name)
    time.sleep(2)
    return

inner()
home(‘cooky‘)

8.示例代碼4：多個裝飾器的執行順序：語法自下而上解析，執行過程為從上到下。記住結論為自上而下執行代碼就可以了

#示例代碼4
def outter1(func):
    print(‘2.this is outter1‘)

    def wrapper1(*args, **kwargs):
        print(‘3.this is wrapper1‘)
        res = func(*args, **kwargs)
        return res
    return wrapper1


def outter2(func):
    print(‘1.this is outter2‘)

    def wrapper2(*args, **kwargs):
        print(‘4.this is wrapper2‘)
        res = func(*args, **kwargs)
        return res
    return wrapper2


@outter1
@outter2
def index():
    print(‘5.this is index‘)


index()

9.示例代碼5：有參裝飾器

#示例代碼5
import time

current_userinfo={‘user‘:None}

def auth(engine = ‘file‘):
    def outter(func):
        def wrapper2(*args, **kwargs):
            if engine == ‘file‘:
                if current_userinfo[‘user‘]:
                    return func(*args, **kwargs)
                user = input(‘please input your username:‘).strip()
                pwd = input(‘please input your password:‘).strip()
                if (user == ‘cooky‘ and pwd == ‘123‘):
                    print(‘login successfully‘)
                    current_userinfo[‘user‘] = user
                    res = func(*args, **kwargs)
                    return res
                else:
                    print(‘login failed‘)
                elif engine == ‘mysql‘:
                    print(‘mysql認證機制‘)
                elif engine == ‘ldap‘:
                    print(‘ldap的認證機制‘)
                else:
                    print(‘不支持改engine‘)
            return wrapper2
    return outter


@auth(engine = ‘ldap‘)
def index():
    print(‘welcome to index page‘)
    time.sleep(3)

index()

10.示例代碼6：wraps裝飾器實現原始函數的文檔和裝飾後函數的文檔一致

#示例代碼6
from functools import wraps

def outter(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        res = func(*args, **kwargs)
        return res
    return wrapper


@outter
def inner():
    """
    this is inner‘s document
    :return:
    """
    print(‘this is inner‘)


print(help(inner))
print(inner.__name__)

python學習5_裝飾器