Decompressing a file retrieved by URL seems too complex

John Nagle nagle at
Thu Aug 12 22:17:06 CEST 2010

    I'm reading a URL which is a .gz file, and decompressing
it.  This works, but it seems far too complex.  Yet
none of the "wrapping" you might expect to work
actually does.  You can't wrap a GzipFile around
an HTTP connection, because GzipFile, reasonably enough,
needs random access, and tries to do "seek" and "tell".
Nor is the output descriptor from gzip general; it fails
on "readline", but accepts "read". (No good reason
for that.) So I had to make a second copy.

				John Nagle

def readurl(url) :
     if url.endswith(".gz") :					
         nd = urllib2.urlopen(url,timeout=TIMEOUTSECS)	
         td1 = tempfile.TemporaryFile()	# compressed file
         td1.write(	# fetch and copy file
         nd.close() # done with network
	td2 = tempfile.TemporaryFile()	# decompressed file # rewind
	gd = gzip.GzipFile(fileobj=td1, mode="rb") # wrap unzip
	td2.write( # decompress file
         td1.close() # done with compressed copy # rewind
         return(td2) # return file object for compressed object
     else :

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