并发下载器

并发下载原理

from gevent import monkey
import gevent
import urllib.request

# 有耗时操作时需要
monkey.patch_all()

def my_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/
111327 bytes received from http://www.baidu.com/.
172054 bytes received from http://www.itheima.com/.
215035 bytes received from http://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

from gevent import monkey
import gevent
import urllib.request

#有IO才做时需要这一句
monkey.patch_all()

def my_downLoad(file_name, url):
    print('GET: %s' % url)
    resp = urllib.request.urlopen(url)
    data = resp.read()

    with open(file_name, "wb") as f:
        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