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

Eli Bendersky eliben at gmail.com
Sat Feb 23 18:15:54 CET 2013

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.SEEKSET, etc.). The constants in the socket module (socket.AFINET, 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.

Thoughts?

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