[Python-Dev] Module version variable

[Guido van Rossum]

On Fri, Mar 18, 2011 at 8:12 PM, Toshio Kuratomi <a.badger at gmail.com> wrote:
> On Fri, Mar 18, 2011 at 07:40:43PM -0700, Guido van Rossum wrote:
>> On Fri, Mar 18, 2011 at 7:28 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
>> > Tres Seaver wrote:
>> >
>> >> I'm not even sure why you would want __version__ in 99% of modules:  in
>> >> the ordinary cases, a module's version should be either the Python
>> >> version (for a module shipped in the stdlib), or the release of the
>> >> distribution which shipped it.
>> >
>> > It's useful to be able to find out the version of a module
>> > you're using at run time so you can cope with API changes.
>> >
>> > I had a case just recently where the behaviour of something
>> > in pywin32 changed between one release and the next. I looked
>> > for an attribute called 'version' or something similar to
>> > test, but couldn't find anything.
>> >
>> > +1 on having a standard place to look for version info.
>>
>> I believe __version__ *is* the standard (like __author__). IIRC it was
>> proposed by Ping. I think this convention is so old that there isn't a
>> PEP for it. So yes, we might as well write it down. But it's really
>> nothing new.
>>
> There is a section in PEP8 about __version__ but it serves a slightly
> different purpose there:
>
> """
> Version Bookkeeping
>
>    If you have to have Subversion, CVS, or RCS crud in your source file, do
>    it as follows.
>
>        __version__ = "$Revision: 88433 $"
>        # $Source$
>
>    These lines should be included after the module's docstring, before any
>    other code, separated by a blank line above and below.
> """

Ah, hm. Yes, that's way outdated. I don't think anyone believe in
marking each file with its revision any more.

I do distinctly recall __version__ being standardized for other
purposes too, but I have no idea how to find that reference... It
probably was well before 2000.

> Personally, I've never found a need to access the repository revision
> programatically from my pyhon applications but I have needed to access the
> API version so it would make sense to me to change the meaning of
> __version__.

Agreed. I don't think that was the only allowed use of __version__ --
just the only mentioned use. (Note the conditional "If you have to
have Subversion, ..." at the start of that paragraph in PEP 8.)

-- 
--Guido van Rossum (python.org/~guido)