Urllib keyerror, confused

[Navtej Singh]

possibly the server did not sent the 'Content-Length' header.

On Feb 2, 2008 5:18 PM, Adam W. <AWasilenko at gmail.com> wrote:
> I took this script: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/83208
> And decided to try it out, it works when I first download a file, and
> when I try to resume a downloaded file, but if the file is already
> downloaded, and I expect to see the print "File already downloaded"
> message come up, I get a keyerror instead:
>
> Traceback (most recent call last):
>   File "C:\Users\Adam\Desktop\ddd.py", line 26, in <module>
>     if int(webPage.headers['Content-Length']) == existSize:
>   File "C:\Python25\lib\rfc822.py", line 384, in __getitem__
>     return self.dict[name.lower()]
> KeyError: 'content-length'
>
> Why did the key disappear?
>
> Here is the code I used (a little modified but functionally the same):
>
> import urllib, os
>
> class myURLOpener(urllib.FancyURLopener):
>     """Create sub-class in order to overide error 206.  This error
> means a
>        partial file is being sent,
>        which is ok in this case.  Do nothing with this error.
>     """
>     def http_error_206(self, url, fp, errcode, errmsg, headers,
> data=None):
>         pass
>
> loop = 1
> dlFile =
> "Okidata_Digital_B4600_Black_and_White_Laser_PrinterlacDetail.jpg"
> 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")
>
> webPage = myUrlclass.open("http://s3-external-1.amazonaws.com/
> wootsaleimages/%s" % dlFile)
>
> #If the file exists, but we already have the whole thing, don't
> download again
> print "flyby"
> if int(webPage.headers['Content-Length']) == existSize:
>     loop = 0
>     print "File already downloaded"
>
> numBytes = 0.0
> numBytes += existSize
> while loop:
>     data = webPage.read(8192)
>     if not data:
>         break
>     outputFile.write(data)
>     numBytes += len(data)
>     print (float(numBytes/int(webPage.headers['Content-Length']))*100)
>
> webPage.close()
> outputFile.close()
>
> for k,v in webPage.headers.items():
>     print k, "=",v
> print "copied", numBytes, "bytes from", webPage.url
> raw_input("Cat")
> --
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>