Python 装饰器

1、开放封闭原则：对扩展开放、对修改是封闭
2、装饰器：装饰它人的，器指的是任意可调用对象，现在的场景装饰器（函数）
被装饰的对象也是函数
原则：1、不修改装饰对象的源代码；2、不修改被装饰对象的调用方式
装饰器的目的：在遵循1,2的前提下为被装饰对象添加上新功能

一、无参装饰器
import time
def timmer(func):
    def inner():
        start = time.time()
        func()
        end = time.time()
        print("run time is %s" %(end - start))
    return inner

@timmer     #相当于index = timmer(index)
def index():
    time.sleep(3)
    print("welcome to index")

index()     #相当于inner()
输出结果：welcome to index
          run time is 3.0010766983032227


改进一：
import time
def timmer(func):
    def inner():
        start = time.time()
        res = func()
        end = time.time()
        print("run time is %s" %(end - start))
        return res
    return inner

@timmer     相当于index = timmer(index)
def index():
    time.sleep(3)
    print("welcome to index")
    return 1111

res = index()    #相当于res = inner()
print(res)
输出结果：welcome to index
          run time is 3.0010766983032227
          1111

改进二：
import time
def timmer(func):
    def inner(*args,**kwargs):
        start = time.time()
        res = func(*args,**kwargs)
        end = time.time()
        print("run time is %s" %(end - start))
        return res
    return inner

@timmer     #相当于index = timmer(index)
def index(name):
    time.sleep(3)
    print("welcome %s to index" %name)
    return 1111

res = index('keke')    #相当于res = inner('keke')
print(res)
输出结果：welcome keke to index
          run time is 3.000697135925293
          1111

二、有参装饰器
import time
def outter(file):
    def welcome(func):
        def inner():
            name = input("name>>:").strip()
            res = func(name)
            if file == 'mysql':
                print("mysql")
            elif file == 'mangodb':
                print('mangodb')
            else:
                print('others!!!')
            return res
        return inner
    return welcome

@outter(file='mangodb')    相当于@welcome  index=welcome(index)
def index(name):
    time.sleep(3)
    print('welcome %s to index' %name)
    return 1111

res = index()
print(res)

输出结果：name>>:keke
          welcome keke to index
          mangodb
         1111