python断点续传

#coding=utf-8
__author__ = 'zengqingming'

import urllib
import os
import sys

default_encoding = 'utf-8'
if sys.getdefaultencoding() != default_encoding:
    reload(sys)
    sys.setdefaultencoding(default_encoding)
#关键在206和416的状态处理
class myURLOpener(urllib.FancyURLopener):
    def http_error_206(self, url, fp, errcode, errmsg, headers, data=None):
        pass

def downloadFile():
    loop = 1
    dlFile = "xxx.apk"
    existSize = 0
    myUrlclass = myURLOpener()
    if os.path.exists(dlFile):
        outputFile = open(dlFile,"ab")
        existSize = os.path.getsize(dlFile)
        #If the file exists, then only download the remainder
        myUrlclass.addheader("Range","bytes=%s-" % (existSize))
    else:
        outputFile = open(dlFile,"wb")

    url = "http://xxx.com/20131213/%s" % dlFile
    print url
    webPage = myUrlclass.open(url)
    responsedCode = webPage.getcode()
    if responsedCode == 416:
        loop = 0
        print "Requested Range not satisfiable"

    contentLength = webPage.headers['Content-Length']
    print "contentLength:%s - existSize:%d " % (contentLength, existSize)
    #If the file exists, but we already have the whole thing, don't download again
    if int(contentLength) == existSize:
        loop = 0
        print "File already downloaded"

    numBytes = 0
    while loop:
        data = webPage.read(8192)
        if not data:
            break
        outputFile.write(data)
        numBytes = numBytes + len(data)
        #print "data:%s" % data
        print "read " , len(data) , " bytes"

    webPage.close()
    outputFile.close()

    for k,v in webPage.headers.items():
        print k, "=",v
    print "code:", webPage.getcode()
    print "copied", numBytes, "bytes from", webPage.url


if __name__ == "__main__":
    downloadFile()