Python实现多线程下载文件的代码实例

#!/usr/bin/python
# -*- coding: utf-8 -*-
# filename: paxel.py
# FROM: http://aspzz.cn/code/view/58/full/
# Jay modified it a little and save for further potential usage.

'''It is a multi-thread downloading tool

    It was developed following axel.
        Author: volans
        E-mail: volansw [at] gmail.com
'''

import sys
import os
import time
import urllib
from threading import Thread

# in case you want to use http_proxy
local_proxies = {'http': 'http://131.139.58.200:8080'}

 
class AxelPython(Thread,urllib.FancyURLopener):
    '''Multi-thread downloading class.

        run() is a vitural method of Thread.
    '''
    def __init__(self,threadname,url,filename,ranges=0,proxies={}):
        Thread.__init__(self,name=threadname)
        urllib.FancyURLopener.__init__(self,proxies)
        self.name = threadname
        self.url = url
        self.filename = filename
        self.ranges = ranges
        self.downloaded = 0

    def run(self):
        '''vertual function in Thread'''
        try:
            self.downloaded = os.path.getsize(self.filename)
        except OSError:
            #print 'never downloaded'
            self.downloaded = 0

        # rebuild start poind
        self.startpoint = self.ranges[0] + self.downloaded

        # This part is completed
        if self.startpoint >= self.ranges[1]:
            print 'Part %s has been downloaded over.' % self.filename
            return

        self.oneTimeSize = 16384  # 16kByte/time
        print 'task %s will download from %d to %d' % (self.name,self.startpoint,self.ranges[1])

        self.addheader("Range","bytes=%d-%d" % (self.startpoint,self.ranges[1]))
        self.urlhandle = self.open(self.url)

        data = self.urlhandle.read(self.oneTimeSize)
        while data:
            filehandle = open(self.filename,'ab+')
            filehandle.write(data)
            filehandle.close()

            self.downloaded += len(data)
            #print "%s" % (self.name)
            #progress = u'r...'

            data = self.urlhandle.read(self.oneTimeSize)

 
def GetUrlFileSize(url,proxies={}):
    urlHandler = urllib.urlopen(url,proxies=proxies)
    headers = urlHandler.info().headers
    length = 0
    for header in headers:
        if header.find('Length') != -1:
            length = header.split(':')[-1].strip()
            length = int(length)
    return length

 
def SpliteBlocks(totalsize,blocknumber):
    blocksize = totalsize / blocknumber
    ranges = []
    for i in range(0,blocknumber - 1):
        ranges.append((i * blocksize,i * blocksize + blocksize - 1))
    ranges.append((blocksize * (blocknumber - 1),totalsize - 1))

    return ranges

 
def islive(tasks):
    for task in tasks:
        if task.isAlive():
            return True
    return False

 
def paxel(url,output,blocks=6,proxies=local_proxies):
    ''' paxel
    '''
    size = GetUrlFileSize(url,proxies)
    ranges = SpliteBlocks(size,blocks)

    threadname = ["thread_%d" % i for i in range(0,blocks)]
    filename = ["tmpfile_%d" % i for i in range(0,blocks)]

    tasks = []
    for i in range(0,blocks):
        task = AxelPython(threadname[i],filename[i],ranges[i])
        task.setDaemon(True)
        task.start()
        tasks.append(task)

    time.sleep(2)
    while islive(tasks):
        downloaded = sum([task.downloaded for task in tasks])
        process = downloaded / float(size) * 100
        show = u'rFilesize:%d Downloaded:%d Completed:%.2f%%' % (size,downloaded,process)
        sys.stdout.write(show)
        sys.stdout.flush()
        time.sleep(0.5)

    filehandle = open(output,'wb+')
    for i in filename:
        f = open(i,'rb')
        filehandle.write(f.read())
        f.close()
        try:
            os.remove(i)
            pass
        except:
            pass

    filehandle.close()

if __name__ == '__main__':
    url = 'http://dldir1.qq.com/qqfile/QQforMac/QQ_V3.1.1.dmg'
    output = 'download.file'
    paxel(url,blocks=4,proxies={})