python 爬虫下载视频加进度条

python爬视频我们以以下代码加注释为例

import  requests
from  contextlib import  closing
import  os

def download_file(url,path):
    #链接地址，获取内容赋值给r
    with closing(requests.get(url,stream=True)) as  r:
        #定义一个1024的字节
        chunk_size=1024
        content_size=int(r.headers['content-length'])
        print('下载开始')
        #开始把内容写入到path中，格式为wb,赋值给 f
        with open(path,"wb") as f:
            n=1;
            #边下载边存硬盘  chunk_size=chunk_size可修改 单位为B
            for  chunl in r.iter_content(chunk_size=chunk_size):
                # 每次下载+1
                loaded=n*1024.0/content_size
                #写入文件
                f.write(chunl)
                print('已下载{0:%}'.format(loaded))
                n+=1
            f.close()
#路径+视频源地址
download_file("https://vd4.bdstatic.com/mda-khkkr38rhxhf5sms/mda-khkkr38rhxhf5sms.mp4", './dome5.mp4')

根据注释可注意一下内容