[Distutils] Specifying version information once

[David Cournapeau]

Jeff Rush wrote:
> A. Cavallo wrote:
>   
>>> No, I would say “too much” here is importing a module not guaranteed to
>>> be installed, for creating something as simple as a version. I'd prefer
>>> the above to be::
>>>
>>>   $ cat _version.py
>>>   # This is an auto-generated file. Use magicbean to update.
>>>   version = "0.9.33"
>>>   $
>>>       
>> Or my preferred way:
>>  $cat foobar/__init__.py
>> __version__ = "0.9.33"
>>
>> and import foobar should not trigger code execution anyway IMHO so
>> $ python -c 'import foobar; print foobar.__version__'
>> 0.9.33
>>     
>
> That doesn't work in all cases.  Your example is of an external query of the
> version of an installed module.  You also need to query the version -before-
> it is installed (during the packaging phase) on sys.path, and also from
> -within- the foobar module itself.  Your code does not handle those cases.  An
> attempt to 'import foobar; print foobar.__version__' from a setup.py inside
> foobar won't find foobar.
>   

That's my experience as well. I am a bit delighted to see that other
people struggled on this, I felt very stupid the first time I tried to
setup this consistently without success.

My current approach is to set up the version in setup.py, but to always
generated a trivial version.py within the package (for the installed
version). The setup.py version is used by paver, the installed version
is used by the sphinx build inside a bootstrapped environment. I think
the situation where you want to build documentation at the same time as
the software happens relatively often, I would be glad to hear of a
better alternative.

cheers,

David