[Python-Dev] [Python-checkins] peps: Pre-alpha draft for PEP 435 (enum). The name is not important at the moment, as

[R. David Murray]

On Sat, 23 Feb 2013 09:15:54 -0800, Eli Bendersky <eliben at gmail.com> wrote:
> On Sat, Feb 23, 2013 at 9:04 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> 
> > On Sat, 23 Feb 2013 08:27:50 -0800
> > Eli Bendersky <eliben at gmail.com> wrote:
> > > > See also http://bugs.python.org/issue16801#msg178542 for another use
> > > > case for named values.
> > > >
> > > > I've seen an awful lot of code that uses global variables or class
> > > > attributes primarily to get name validation on constant values, and I
> > > > think all of that code would be a prime candidate for using Named
> > Values.
> > > > Some of them are also enum-like, but many of them are not.  So I'm with
> > > > Nick on this one.
> > >
> > > Any suggestions for places in the stdlib where enums could come useful
> > will
> > > be most welcome
> >
> > The constants in the os module (os.SEEK_SET, etc.).
> > The constants in the socket module (socket.AF_INET, etc.).
> > And so on :-)
> >
> 
>  Hmm, constants such as os.SEEK_* which serve as *inputs* to stdlib rather
> than outputs can actually be a good candidate for enum without worrying
> about backwards compatibility.
> 
> The reason I make the *input* vs. *output* distinction, is that for stdlib
> code that returns values, the user may rely on their numeric values and if
> we switch to enum code will break. However, for os.SEEK_* this is not the
> case. Thee can be aliases for enums:
> 
> class SeekKind(Enum):
>   SEEK_SET = 0
>   SEEK_CUR = 1
>   SEEK_END = 2
> 
> SEEK_SET = SeekKind.SEEK_SET
> ...
> 
> lseek() can be changed to call 'int' on its input, and now os.SEEK_* gain
> useful string representations when printed.

Eh, what?  Why does int have to be called?  (Hrm, I guess I'd better
read the PEP before making any more comments :)

I'm preferring Named Values more and more.  And I'm just as interested
in the returned values case as I am in the input case (as the errno
example indicates).

--David