2-2-08 函数-闭包

闭包，简而言之就是将数据封装在一个包（区域）中，使用时再去里面取。（本质上 闭包是基于函数嵌套搞出来一个中特殊嵌套）

• 闭包应用场景1：封装数据防止污染全局。

def func(age):
    name = "武沛齐"

    def f1():
        print(name, age)

    def f2():
        print(name, age)

    def f3():
        print(name, age)

    f1()
    f2()
    f3()

func(123)

• 闭包应用场景2：封装数据封到一个包里，使用时在取。

def task(arg):
    def inner():
        print(arg)
    return inner

v1 = task(11)
v2 = task(22)
v3 = task(33)
v1()
v2()
v3()

def task(arg):
    def inner():
        print(arg)
    return inner

inner_func_list = []
for val in [11,22,33]:
    inner_func_list.append( task(val) )
    
inner_func_list[0]() # 11
inner_func_list[1]() # 22
inner_func_list[2]() # 33

""" 基于多线程去下载视频 """
from concurrent.futures.thread import ThreadPoolExecutor

import requests


def download_video(url):
    res = requests.get(
        url=url,
        headers={
            "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36 FS"
        }
    )
    return res.content


def outer(file_name):
    def write_file(response):
        content = response.result()
        with open(file_name, mode='wb') as file_object:
            file_object.write(content)

    return write_file


POOL = ThreadPoolExecutor(10)

video_dict = [
    ("东北F4模仿秀.mp4", "https://aweme.snssdk.com/aweme/v1/playwm/?video_id=v0300f570000bvbmace0gvch7lo53oog"),
    ("卡特扣篮.mp4", "https://aweme.snssdk.com/aweme/v1/playwm/?video_id=v0200f3e0000bv52fpn5t6p007e34q1g"),
    ("罗斯mvp.mp4", "https://aweme.snssdk.com/aweme/v1/playwm/?video_id=v0200f240000buuer5aa4tij4gv6ajqg")
]
for item in video_dict:
    future = POOL.submit(download_video, url=item[1])
    future.add_done_callback(outer(item[0]))

POOL.shutdown()