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

[Antoine Pitrou]

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.

Regards

Antoine.