简单示例代码：

# 描述：爬取网页中的图片，
#     此处就给一些图片的连接，对图片下载。
#     采用并发的方式
# 此处给好的图片链接分别为：

import urllib.request
import gevent
from gevent import monkey

monkey.patch_all()


# def main():
#     req = urllib.request.urlopen("https://rpic.douyucdn.cn/live-cover/roomCover/cover_update/2019/09/20/11aa0f39ee5bd02e402cc90394e9bde4.jpg")
#     img_content = req.read()

#     with open('1.jpg', 'wb') as f:
#         f.write(img_content)

# 下载图片
def downpic(url, filename):
    req = urllib.request.urlopen(url)
    img_content = req.read()
    with open(filename, 'wb') as f:
        f. write(img_content)

# 用协程的方式。
# gevent
gevent.joinall([
    gevent.spawn(downpic, "https://rpic.douyucdn.cn/live-cover/roomCover/cover_update/2019/09/20/xxxcc90394e9bde4.jpg", '1.jpg'),
    gevent.spawn(downpic, "https://rpic.douyucdn.cn/live-cover/roomCover/cover_update/2019/09/06/xx2f16522f1dc7cf.jpg", '2.jpg'),
    gevent.spawn(downpic, "https://rpic.douyucdn.cn/asrpic/190924/161xx9.png", '3.png')
])