装饰器181029

Posted 2021-01-16 l-dongf

装饰器（语法糖decorator）定义

• 装饰器本质上是函数
• 装饰器的功能是为了装饰其他函数

• 为其他函数添加附加功能

  装饰器特定的原则

• 不能修改被装饰函数的原代码

• 不能修改被装饰函数的调用方式

  装饰器相关知识点

• 函数即“变量”
• 高阶函数
  • 把一个函数名当做实参传给另外一个函数(在不修改函数的原代码为函数添加新功能)
  • 返回值中包含函数名（不修改调用方式）

• 嵌套函数

  高阶函数 + 嵌套函数 = 装饰器

  高阶函数示例代码

# Author:Li Dongfei
import time
def bar():
    time.sleep(3)
    print("in the bar")
def test1(func):
    start_time = time.time()
    func()
    stop_time = time.time()
    print("the func run time is %s" %(stop_time - start_time))
test1(bar)

不修改调用方式代码示例

# Author:Li Dongfei
import time
def bar():
    time.sleep(3)
    print("in the bar")
def test2(func):
    print(func)
    return func
bar = test2(bar)
bar()

函数的嵌套

# Author:Li Dongfei
def foo():
    print("in the foo")
    def bar():
        print("in the bar")
    bar()
foo()

装饰器1

# Author:Li Dongfei
import time
def timer(func):  #func == test1的内存地址
    def deco():
        start_time = time.time()
        func()  #run test1()
        stop_time = time.time()
        print("the func run time is %s" %(stop_time - start_time))
    return deco
def test1():
    time.sleep(3)
    print("in the test1")
def test2():
    time.sleep(3)
    print("in the test2")
test1 = timer(test1)
test1()

装饰器2

# Author:Li Dongfei
import time
def timer(func):  #func == test1的内存地址
    def deco():
        start_time = time.time()
        func()  #run test1()
        stop_time = time.time()
        print("the func run time is %s" %(stop_time - start_time))
    return deco
@timer  # test1 = timer(test1)
def test1():
    time.sleep(3)
    print("in the test1")
@timer
def test2():
    time.sleep(3)
    print("in the test2")
test1()
test2()

带参数传递的装饰器

# Author:Li Dongfei
import time
def timer(func):
    def deco(*args,**kwargs):
        start_time = time.time()
        func(*args,**kwargs)
        stop_time = time.time()
        print("the func run time is %s" %(stop_time - start_time))
    return deco
@timer
def test1():
    time.sleep(1)
    print("in the test1")
@timer  #test2 = timer(test2) = deco  ,  test2(name) == deco(name)
def test2(name):
    time.sleep(2)
    print("test2:",name)
test1()
test2("dongfei")

装饰器示例：实现验证功能

# Author:Li Dongfei
import time
user,passwd = 'dongfei','123456'
def auth(auth_type):
    def outer_wrapper(func):
        def wrapper(*args,**kwargs):
            username = input("Username: ").strip()
            password = input("Password: ").strip()
            if auth_type == "local":
                if user == username and passwd == password:
                    print("login successful")
                    res = func(*args,**kwargs)
                    return res  #返回被装饰函数的执行结果
                else:
                    exit("login failure")
            elif auth_type == "ldap":
                print("ldap认证")
        return wrapper
    return outer_wrapper
def index():
    print("welcome to index page")
@auth(auth_type="local")  # home = wrapper()
def home():
    print("welcome to home page")
    return "from home"
@auth(auth_type="ldap")
def bbs():
    print("welcome to bbs page")
index()
print(home())
bbs()