装饰器

一、什么是装饰器

装饰器：

• 不修改被装饰对象的源代码
• 不修改被装饰对象的调用方式

import time


# 初级下载版
def download_movie():
    print('开始下载电影...')
    time.sleep(3)
    print('电影下载成功...')


start_time = time.time()
print(time.time())
download_move()
end_time = time.time()
print(time.time())
print(f'消耗时间：{start_time - end_time}')

# 加入计时函数
def download_movie():
    print('开始下载电影....')
    time.sleep(3)
    print('完成下载电影....')


def time_timer(func):
    def timer_inner():
        start_time = time.time()
        func()
        end_time = time.time()
        print(f'下载用时：{end_time - start_time}')
    return timer_inner

download_movie = time_timer(download_movie)
download_movie()

# 问题1：被装饰对象有返回值
# 下载电影功能
def download_movie():
    print('开始下载电影...')
    time.sleep(3)
    print('下载完毕...')
    return '小泽.mp4'


def time_timer(func):
    def inner():
        start_time = time.time()
        res = func()
        end_time = time.time()
        print(f'消耗了：{end_time - start_time}')
        return res
    return inner

download_movie = time_timer(download_movie)
download_movie()

# 问题2：被装饰对象 有参数
def download_movie():
    print('下载开始....')
    time.sleep(3)
    print('下载完成')
    return '小泽.mp4'

def time_timer(func):
    def timer_inner(*args, **kwargs):
        start_time = time.time()
        res = func(*args, **kwargs)
        end_time = time.time()
        print(f'耗费时间：{end_time - start_time}')
        return res
    return timer_inner

download_movie = time_timer(download_movie)
download_movie()

# 二、装饰器的模板

模板：
def outer(func):
    def inner(*args,**kwargs):
        res=func(*args,**kwargs)
        return res
    return inner