网络重新连接时，Python urllib2 恢复下载不起作用 [英] Python urllib2 resume download doesn't work when network reconnects

问题描述

我正在使用 urllib2 制作恢复下载器，大致基于 这个 方法.我可以结束程序并重新启动它，它会从停止的地方开始下载，下载的文件大小与一次下载的文件大小相同.

I'm using urllib2 to make a resuming downloader, roughly based on this method. I can end the program and re-start it, and it starts downloading where it left off, downloading the file that ends up the same size as if it were downloaded all at once.

但是，我在禁用和重新启用网络时对其进行了测试，但无法正确下载.文件大小最终超过文件应有的大小，并且文件无法正常工作.是不是我遗漏了什么，或者这可能是 urllib2 的错误?

However, I have tested it when disabling and reenabling network, and it doesn't download correctly. The file size ends up longer than the file should be, and the file doesn't work correctly. Is there something I missed, or could this be a urllib2 bug?

    import urllib2
    opener = urllib2.build_opener();

    self.count = 0 # Counts downloaded size.
    self.downloading = True
    while (not(self.success) and self.downloading):
        try:
            self.Err = ""
            self._netfile = self.opener.open(self.url)
            self.filesize = float(self._netfile.info()['Content-Length'])

            if (os.path.exists(self.localfile) and os.path.isfile(self.localfile)):
                self.count = os.path.getsize(self.localfile)
            print self.count,"of",self.filesize,"downloaded."
            if self.count >= self.filesize:
                #already downloaded
                self.downloading = False
                self.success = True
                self._netfile.close()
                return

            if (os.path.exists(self.localfile) and os.path.isfile(self.localfile)):
                #File already exists, start where it left off:
                #This seems to corrupt the file sometimes?
                self._netfile.close()
                req = urllib2.Request(self.url)
                print "file downloading at byte: ",self.count
                req.add_header("Range","bytes=%s-" % (self.count))
                self._netfile = self.opener.open(req)
            if (self.downloading): #Don't do it if cancelled, downloading=false.
                next = self._netfile.read(1024)
                self._outfile = open(self.localfile,"ab") #to append binary
                self._outfile.write(next)
                self.readsize = desc(self.filesize) # get size mb/kb
                self.count += 1024
                while (len(next)>0 and self.downloading):
                    next = self._netfile.read(1024)
                    self._outfile.write(next)
                    self.count += len(next)
                self.success = True
        except IOError, e:
            print e
            self.Err=("Download error, retrying in a few seconds: "+str(e))
            try:
                self._netfile.close()
            except Exception:
                pass
            time.sleep(8) #Then repeat

推荐答案

我在 IOError 处理程序中添加了 self._outfile.close() 和 self._netfile.close() ，这似乎已经修复了它.我猜这个错误是由于再次打开追加而不关闭它引起的.

I added self._outfile.close() with the self._netfile.close() in the IOError handler, that seems to have fixed it. I guess this error was caused by opening for appending again without closing it.

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