How to create a socket.socket() object from a socket fd?

Antoon Pardon antoon.pardon at
Mon Jan 23 11:02:22 EST 2017

Op 22-01-17 om 01:52 schreef Grant Edwards:
> Newsgroups: gmane.comp.python.general
> From: Grant Edwards <grant.b.edwards at>
> Subject: Re: How to create a socket.socket() object from a socket fd?
> References: <o60naq$bbm$1 at> <o60o2r$6cd$1 at> <c7e3116f-6e9c-5343-6f82-c491fb917800 at>
> Followup-To: 
> <rant>
> I'm still baffled why the standard library fromfd() code dup()s the
> descriptor.
> According to the comment in the CPython sources, the author of
> fromfd() is guessing that the user wants to be able to close the
> descriptor separately from the socket.
> If the user wanted the socket object to use a duplicate descriptor for
> some reason, the caller should call os.dup() -- it's only _eight_
> keystrokes.  Eight keystrokes that makes it obvious to anybody reading
> the code that there are now two descriptors and you have to close both
> the original descriptor and the socket.
> When you create a Python file object from a file descriptor using
> os.fdopen(), does it dup the descriptor?  No.  Would a reasonable
> person expect socket.fromfd() to duplicate the descriptor?  No.
> Should it?
> No.

The standard response to issues like this is:

   A foolish consistency is the hobgoblin of little minds

Antoon Pardon

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