Just test:

>>> socket.gethostbyname('www.google.com')

'216.239.39.99'

>>> socket.gethostbyaddr('216.239.39.99')

Traceback (most recent call last):
  File "<interactive input>", line 1, in ?
herror: (11004, 'host not found')

Don't know why. Maybe of this strange akadns-stuff?!?!
He struggles around for quite a time before he comes to 
the error, maybe to much or cyclic input.

Cheers,
Spikeee

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This is not a bug/feature of the python socket module, but of DNS 
itself. DNS uses a seperate tree to find the name associated with 
an IP adres, there is no entry for the address associated with 
www.google.com.

The same feature can be observed from the command-line:

$ nslookup www.google.com ns.xs4all.nl
Server:         ns.xs4all.nl
Address:        194.109.6.66#53

Non-authoritative answer:
www.google.com  canonical name = www.google.akadns.net.
Name:   www.google.akadns.net
Address: 216.239.59.99

$ nslookup 216.239.59.99 ns.xs4all.nl
Server:         ns.xs4all.nl
Address:        194.109.6.66#53

** server can't find 99.59.239.216.in-addr.arpa: NXDOMAIN

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Good answer. Since this is not a bug I suggest Gert or 
someone removes it from the bug list. Does anyone know of 
another forum for these kind of common non-bug questions? I 
could only think of posting to comp.lang.python/activestate's 
python-list for archival purpose.




...johahn

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Closed as 3rd-party, won't fix, which is the closest thing we 
have to "it's not a bug, but it's not Python's doing even if it 
were" <wink>.  Asking for a tutorial about anything on c.l.py 
will usually get a decent response (Python-related or not).