Three is the decorator -----

Decorator

1. Open Closed Principle

   • To expand is open, allowing the code to expand, adding new features
   • Modifications are closed, you can not modify the source code and the function is called

2. Decorator

   • Without changing the original decorative function source code and is called by the premise, to add additional functionality

     # 版本一，测试每个函数都要写一遍代码
     import time
     def func1():
         time.sleep(2)    # 暂停2秒
         print('测试延迟')
     time1 = time.time()   # 返回的格林威治时间，是此时此刻距离1970年1月1日0时0分0秒的时间秒数，也叫时间戳
     func1()
     time2 = time.time()
     print(time2-time1)

     # 版本二 只能测试特定的函数
     import time
     def func1():
         time.sleep(2)
         print('测试延迟')
     def ceshi():
         time1 = time.time()
         func1()
         time2 = time.time()
         print(time2-time1)
     ceshi()

     # 版本三，虽然没有改变原函数的代码，但是改变了执行方式，不符合开放封闭原则
     import time
     def func1():
         time.sleep(2)
         print('测试延迟')
     def ceshi(func):
         time1 = time.time()
         func()
         time2 = time.time()
         print(time2-time1)
     ceshi(func1)

     #版本四，实施真正的开放封闭原则：装饰器
     import time
     def func1():
         time.sleep(2)
         print('测试延迟')
     def timer(func):
         def ceshi():
             time1 = time.time()
             func()
             time2 = time.time()
             print(time2-time1)
         return ceshi
     func1 = timer(func1)
     func1()

     #带返回值的装饰器
     import time
     def func1():
         time.sleep(2)
         print('测试延迟')
         return '测试成功'
     def timer(func):
         def ceshi():
             time1 = time.time()
             ret = func()
             time2 = time.time()
             print(time2-time1)
             return ret
         return ceshi
     func1 = timer(func1)
     print(func1())

     # 被装饰函数带参数的装饰器
     import time
     def func1(name):
         time1 = time.sleep(2)
         print(f'{name}测试延迟')
         return f'{name}测试成功'
     def timer(func):
         def ceshi(name):
             time1 = time.time()
             ret = func(name)
             time2 = time.time()
             print(time2-time1)
             return ret
         return ceshi
     func1=timer(func1)
     print(func1('太上老君'))

     # 被装饰函数不定参数的装饰器
     import time
     def func1(*args,**kwargs):
         time.sleep(2)
         print(f'{args}测试延迟')
         return f'{args,kwargs}测试成功'
     def timer(func):
         def ceshi(*args,**kwargs):
             time1 = time.time()
             ret = func(*args,**kwargs)
             time2 = time.time()
             print(time2-time1)
             return ret
         return ceshi
     func1 = timer(func1)
     print(func1('太上老君','元始天尊',我叫='通天教主'))

     #标准装饰器：语法糖
     import time
     def timer(func):   #func=func1
         def ceshi(*args,**kwargs):
             # args = ('太上老君', '元始天尊')
             # kwagrs = {'我叫'； '通天教主'}
             time1 = time.time()
             ret = func(*args,**kwargs)   
             time2 = time.time()
             print(time2-time1)
             return ret
         return ceshi
     @timer    # 相当于 func1 = timer(func1),没有特殊意义，为了简化
     def func1(*args,**kwargs):
         time.sleep(2)
         print(f'{args,kwargs}测试延迟')
         return f'{args,kwargs}测试成功'
     print(func1('太上老君', '元始天尊', 我叫='通天教主'))