[Python-Dev] SEEK_* constants in io and os

[Antoine Pitrou]

Le Mon, 2 Sep 2013 15:45:22 +0200,
Antoine Pitrou <solipsis at pitrou.net> a écrit :
> Le Mon, 2 Sep 2013 06:18:31 -0700,
> Eli Bendersky <eliben at gmail.com> a écrit :
> > On Mon, Sep 2, 2013 at 1:24 AM, Antoine Pitrou <solipsis at pitrou.net>
> > wrote:
> > 
> > > Le Sun, 1 Sep 2013 18:02:30 -0700,
> > > Eli Bendersky <eliben at gmail.com> a écrit :
> > > > Hello,
> > > >
> > > > I was looking at the possibility of replacing the SEEK_*
> > > > constants by IntEnums, and the first thing that catches
> > > > attention is that these constants are defined in both Lib/os.py
> > > > and Lib/io.py; both places also recently started supporting
> > > > SEEK_HOLE and SEEK_DATA (though here io refers to os.SEEK_HOLE
> > > > and os.SEEK_DATA).
> > >
> > > What is the runtime cost of doing so? os is a fundamental module
> > > that is imported by almost every Python program.
> > >
> > 
> > Theoretically, it should be very low given that we just need to add
> > an import and define one class. os already does a number of things
> > in its toplevel (mostly a few imports which transitively do other
> > things). Compounded with import caching, since this is done just
> > once per run, doesn't seem like a problem.
> > 
> > Empirically, I tried measuring it but I can't discern a difference
> > with/without translating SEEK_* to enums. There's a fluctuation of
> > ~1usec which I can't distinguish from noise. Let me know if you have
> > a good methodology of benchmarking these things
> 
> How did you get that result? You have to remove to "os" from
> sys.modules before importing it again, otherwise "import os" will
> simply return the already imported module.

Oh and remove "enum" too...

Regards

Antoine.