Python basis 11 / decorator

Python basis 11 / decorator

Content Outline

1. decorator

1. decorator

1.1 Open Closed Principle

扩展是开放的(增加新功能)
修改源码是封闭的(修改已经实现的功能)

在不修改源码及调用方式的前提下额外增加新的功能

1.2 decorator

用来装饰的工具

版一:
import time
starrt_time = time.time()
def func():
    time.sleep(2)  #睡眠 (模拟网络延时)
    print("你好")
func()
print(time.time()-start_time)

# start_time = time.time()
# def foo():
#     time.sleep(3) #睡眠 (模拟网络延时)
#     print("我是小明,我飞的比你高")
# foo()
# print(time.time() - start_time)

版二:
def times(f):
    start_time = time.time()
    f()
    print(time.time() - start_time)
def foo():
    time.sleep(3)
    print("我好")
    
def func():
    time.sleep(1)
s = func
func = times
func(s)

版三 (初识版装饰器)
def times(f):
    def inner():
        start_time = time.time()
        f()
        print(time.time() - start_time)
    return inner 
def foo():
    time.sleep(1)
    print("大家好")
foo = times(foo)
foo()

版四 (第二版装饰器)
def wrapper():
    def inner():
        print(1)
    return inner  #切记inner后面不要加括号
def func():
    print(2)
func = wrapper(func)
func()


# def wrapper(f):
#     def inner():
#         print(f)
#     return inner  # 切记不要加括号
# wrapper("alex")

# def wrapper(f):
#     def inner():
#         f()
#     return inner  # 切记不要加括号
#
# def func():
#     print("这是func函数,李业还是不行")
# func = wrapper(func)
# func()        

def wrapper(f):
    def inner(*args,**kwargs):
        f(*args,**kwargs)   #func("  ")
    return inner   #切记不要加括号()
def func(*args,**kwargs):
    print(f"haodi{args}")
func = wrapper(func)
func("nihao","wohao")

low版
import time
def wrapper(f):
    def inner(*args,**kwargs):
        "被装饰前"
        start_time = time.time()
        f(*args,**kwargs)   #func()
        print(time.time() - start_time)
        "被装饰后"
    return inner 
def func(*args,**kwsrgs):
    print("nihao")
    time.sleep(2)
func = wrpper(func)
func("nihao","wohao")

高级
import time
def wrapper(f):
    def inner(*args,**kwargs):
        "被装饰前"
        start_time = time.time()
        f(*args,**kwargs)   #func()
        print(time.time() - start_time)
        "被装饰后"
    return inner 
@wrapper   #相当于 func=wrapper(func)
def func(*args,**kwsrgs):
    print("nihao")
    time.sleep(2)
func("nihao","wohao")

语法糖  --- 甜 @
语法糖必须放在被装饰的函数的正上方

# import time
# def wrapper(f):
#     def inner(*args,**kwargs):
#         "被装饰前"
#         start_time = time.time()
#         ret = f(*args,**kwargs) # func("alex")
#         print(time.time() - start_time)
#         "被装饰后"
#         return ret
#     return inner  # 切记不要加括号
#
# @wrapper  # func = wrapper(func)
# def func(*args,**kwargs):
#     print(f"这是{args}函数,李业还是不行")
#     time.sleep(2) #模拟网络延时
#     return "alex"
# print(func())   

Decorative return value passed

login_dic = {
    "username": None,
    "flag": False
}

def auth(f):
    def inner(*args,**kwargs):
        if login_dic["flag"]:
            return f()
        else:
            return login()
    return inner

@auth    #index = auth(index)
def index():
    print(f"这是{login_dic['username']}主页")
    return "主页没有内容"

def login():
    print("这是一个登录页面")
    user = input("username:")
    pwd = input("password:")
    if user == "baoyuan" and pwd == "baoyuan123":
        login_dic["flag"] = True
        login_dic["username"] = user
        return
    else:
        return "用户名或密码错误!"
@auth    #comment = auth(comment)
def comment():
    print(f"这是{login_dic['username']}评论")

while not login_dic["flag"]:
    print(comment())

2. Exercise today

# 1.整理今天的笔记以及课上代码,以及代码的执行流程.
#
# 2.将模拟博客园使用装饰器进行编写.
# login_dic = {
#     "username": None,
#     "flag": False
# }
# def auth(f):
#     def inner(*args,**kwargs):
#         if login_dic["flag"]:
#             return f()
#         else:
#             return login()
#     return inner
#
# @auth
# def index():
#     print(f"这是{login_dic['username']}主页")
#     return "主页没有内容"
#
# def login():
#     print("这是一个登录页面")
#     user = input("username:")
#     pwd = input("password:")
#     if user == "baoyuan" and pwd == "baoyuan123":
#         login_dic["flag"] = True
#         login_dic["username"] = user
#         return "登录成功!"

#     else:
#         return "用户名或密码错误!"
#
# @auth
# def comment():
#     return f"这是{login_dic['username']}评论"
# #
# while not login_dic["flag"]:
#     if login() == "登录成功!":
#         print("登陆成功!")
#         print(comment())
#     else:
#         print(login())
#
# 3.看代码写结果：
# def wrapper(f):
#     def inner(*args,**kwargs):
#         print(111)
#         ret = f(*args,**kwargs)
#         print(222)
#         return ret
#     return inner
#
# def func():
#     print(333)
#
# print(444)
# func()
# print(555)
# 444
# 333
# 555
#
# 4.编写装饰器, 在每次执行被装饰函数之前打印一句’每次执行被装饰函数之前都得先经过这里’.
# def wrapper(func):
#     def inner():
#         print("每次执行被装饰函数之前都得先经过这里")
#         func()
#     return inner
# @wrapper
# def func():
#     print("这是被装饰的函数")
# func()
#
5.为函数写一个装饰器，把函数的返回值 + 100然后再返回。
# def wrapper(func):
#     def inner():
#         ret = func()
#         return ret+100
#     return inner
# @wrapper
# def func():
#     return 7
# result = func()
# print(result)
#
6.请实现一个装饰器，通过一次调用使被装饰的函数重复执行5次。
# def wrapper(func):
#     def inner():
#         for i in range(5):
#             func()
#     return inner
# @wrapper
# def func():
#     return "这是被装饰的函数"
# func()
#
# 7.请实现一个装饰器，每次调用函数时，将被装饰的函数名以及调用被装饰函数的时间节点写入文件中。
# 可用代码：
# import time
# struct_time = time.localtime()
# print(time.strftime("%Y-%m-%d %H:%M:%S", struct_time))  # 获取当前时间节点
#
# def func():
#     print(func.__name__())
# 函数名通过： 函数名.__name__获取。
# import time
# def wrapper(func):
#     def inner():
#         struct_time = time.localtime()
#         a = time.strftime("%Y-%m-%d %H:%M:%S", struct_time)
#         b = func.__name__
#         with open("info","a",encoding="utf-8") as f:
#             f.write(f'调用时间点:{a},函数名:{b}\n')
#     return inner
# @wrapper
# def func():
#     print("这是被装饰的函数")
# func()