[Python-Dev] PEP 396, Module Version Numbers

[Michael Foord]

On 07/04/2011 12:59, Nick Coghlan wrote:
> On Thu, Apr 7, 2011 at 9:10 PM, Michael Foord<fuzzyman at voidspace.org.uk>  wrote:
>> I really dislike this way of specifying the version. For a start it is
>> really ugly.
>>
>> More importantly it means the version information is *only* available if the
>> package has been installed by "packaging", and so isn't available for the
>> parts of my pre-build process like building the documentation (which import
>> the version number to put into the docs).
>>
>> Currently all my packages have the canonical version number information in
>> the package itself using:
>>
>>     __version__ = '1.2.3'
>>
>> Anything that needs the version number, including setup.py for upload to
>> pypi, has one place to look for it and it doesn't depend on any other tools
>> or processes. If switching to "packaging" prevents me from doing this then
>> it will inhibit me using "packaging".
>>
>> What I may have to do is use a python script that will generate the static
>> metadata, which is not such a bad thing I guess as it will only need to be
>> executed at package build time. I won't be switching to that horrible
>> technique for specifying versions within my packages though.
> It sounds like part of the PEP needs another trip through
> distutils-sig. An informational PEP really shouldn't be advocating
> standard library changes, but it would make sense for this point of
> view to inform any updates to PEP 386 (the version handling
> standardisation PEP).
>
> As I see it, there appear to be two main requests:
> 1. Normalised version parsing and comparison should be available even
> if packaging itself is not installed (e.g. as part of pkgutil)
> 2. packaging should support extraction of the version metadata from
> the source files when bundling a package for distribution
>
> On point 2, rather than requiring that it be explicitly requested, I
> would suggest the following semantics for determining the version when
> bundling a package ready for distribution:
>
> - if present in the metadata, use that
> - if not present in the metadata, look for __version__ in the module
> source code (or the __init__ source code for an actual package)
> - otherwise warn the developer that no version information has been
> provided so it is automatically being set to "0.0.0a0"
>
This sounds good to me.

As an added consideration the suggested technique may not work for tools 
like py2exe / py2app, embedded python and alternative implementations - 
which may not have the full "pacakging" machinery available.

All the best,

Michael Foord


> Cheers,
> Nick.
>


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