python 使用requests模块进行 视频文件的下载

公司项目需要下载一批视频文件， 格式是mp4和mkv的，就借助request模块进行了下载，前提是源服务器返回文件的大小，以及可以接受 请求头headers中带有Range参数
以下是下载逻辑：

resp = requests.head(url=real_video_url)
headers = {}
try:
    totalfilesize = int(resp.headers['Content-Length'])
except Exception as e:
    print(e.args)

if not os.path.exists(real_video_download_path):
    with open(real_video_download_path, 'ab+') as f:
        pass

fsize1 = os.path.getsize(real_video_download_path)
flag = True
while True:
    if flag:
        try:
            fsize1 = os.path.getsize(real_video_download_path)
            headers['Range'] = 'bytes=%d-' % fsize1
            resp = requests.get(url=real_video_url, headers=headers, stream=True, timeout=20)
            with open(real_video_download_path, 'ab+') as f:
                for chunk in resp.iter_content(chunk_size=4096):
                    if resp.status_code == 206:
                        if chunk:
                            f.write(chunk)
                    elif os.path.getsize(real_video_download_path) >= totalfilesize:
                        # 出现这种情况，就说明已经下载完毕
                        flag = False
                        return real_video_download_path
                    else:
                        # 出现异常
                        time.sleep(3)
                        break
        except Exception as e:
            print(e.args)
    else:
        break