4-10

并发下载器

并发下载原理

fromgeventimportmonkeyimportgeventimporturllib.request# 有耗时操作时需要monkey.patch_all()defmy_downLoad(url):print('GET: %s'% url)    resp = urllib.request.urlopen(url)    data = resp.read()    print('%d bytes received from %s.'% (len(data), url))gevent.joinall([        gevent.spawn(my_downLoad,'http://www.baidu.com/'),        gevent.spawn(my_downLoad,'http://www.itcast.cn/'),        gevent.spawn(my_downLoad,'http://www.itheima.com/'),])

运行结果

GET: http://www.baidu.com/GET: http://www.itcast.cn/GET: http://www.itheima.com/111327bytes receivedfromhttp://www.baidu.com/.172054bytes receivedfromhttp://www.itheima.com/.215035bytes receivedfromhttp://www.itcast.cn/.

从上能够看到是先发送的获取baidu的相关信息，然后依次是itcast、itheima，但是收到数据的先后顺序不一定与发送顺序相同，这也就体现出了异步，即不确定什么时候会收到数据，顺序不一定

实现多个视频下载

fromgeventimportmonkeyimportgeventimporturllib.request#有IO才做时需要这一句monkey.patch_all()defmy_downLoad(file_name, url):print('GET: %s'% url)    resp = urllib.request.urlopen(url)    data = resp.read()withopen(file_name,"wb")asf:        f.write(data)    print('%d bytes received from %s.'% (len(data), url))gevent.joinall([        gevent.spawn(my_downLoad,"1.mp4",'http://oo52bgdsl.bkt.clouddn.com/05day-08-%E3%80%90%E7%90%86%E8%A7%A3%E3%80%91%E5%87%BD%E6%95%B0%E4%BD%BF%E7%94%A8%E6%80%BB%E7%BB%93%EF%BC%88%E4%B8%80%EF%BC%89.mp4'),        gevent.spawn(my_downLoad,"2.mp4",'http://oo52bgdsl.bkt.clouddn.com/05day-03-%E3%80%90%E6%8E%8C%E6%8F%A1%E3%80%91%E6%97%A0%E5%8F%82%E6%95%B0%E6%97%A0%E8%BF%94%E5%9B%9E%E5%80%BC%E5%87%BD%E6%95%B0%E7%9A%84%E5%AE%9A%E4%B9%89%E3%80%81%E8%B0%83%E7%94%A8%28%E4%B8%8B%29.mp4'),])

上面的url可以换为自己需要下载视频、音乐、图片等网址