06-python进阶-多线程下载器练手

我们需要用python 写一个多线程的下载器

我们要先获取这个文件的大小 然后将其分片 然后启动多线程 分别去下载 然后将其拼接起来

#!/usr/bin/env python
#coding:utf-8
import  requests

from  multiprocessing.dummy import Pool as ThreadPool

class my_download(object):

    def __init__(self,URL):
        self.url = URL
        self.thread_num = 5
        self.file_nume = URL.split('/')[-1]
        url_headers = requests.head(self.url)
        self.total = int(url_headers.headers['Content-Length'])
        print self.total
        #print type('total is %s' % (self.total))

    def get_file_range(self):
        ranges = []

        download_num = int(self.total/self.thread_num)
        print download_num
        for i in range(self.thread_num):
            if i == self.thread_num-1:
                ranges.append((download_num*i,''))
            else:
                ranges.append((download_num*i,download_num*(i+1)))
        return ranges


    def download_file(self,val):
        f = open(self.file_nume, 'w')
        r = requests.get(self.url, headers={'Range': 'Bytes=%s-%s' % val, 'Accept-Encoding': '*'})
        f.seek(val[0])
        f.write(r.content)
        return  f

    def run(self):

        file_list = self.get_file_range()
        #print file_list
        Pool = ThreadPool(4)
        res = map(self.download_file,file_list)

        for i in res:
            i.close()

        Pool.close()
        Pool.join()


url = "https://img3.doubanio.com/icon/up121443072-1.jpg"
downloader = my_download(url)
downloader.run()