[Python-Dev] PEP 396, Module Version Numbers

[P.J. Eby]

At 03:24 PM 4/10/2011 +0000, exarkun at twistedmatrix.com wrote:
>On 04:02 am, pje at telecommunity.com wrote:
>>At 08:52 AM 4/10/2011 +1000, Ben Finney wrote:
>>>This is an often-overlooked case, I think. The unspoken assumption is
>>>often that ``setup.py`` is a suitable place for the overall version
>>>string, but this is not the case when that string must be read by
>>>non-Python programs.
>>
>>If you haven't used the distutils a lot, you might not realize that 
>>you can do this:
>>
>>$ python setup.py --version
>>0.6c12
>>
>>(The --name option also works, and they can be used together -- the 
>>answers will be on two separate lines.)
>
>This only works as long as setup.py is around - which it typically 
>no longer is after installation is complete.
>
>And though it's common and acceptable enough to launch a child 
>process in a shell script in order to get some piece of information, 
>it isn't as pleasant in a Python program.  Can you get this version 
>information out of setup.py without running a child process and 
>without monkey-patching sys.argv and sys.stdout?

I was replying to the part above about "setup.py ...  must be read by 
non-Python programs".

In other words, I thought the question was, "given a 
not-yet-installed source package, how can we find the version number 
without writing Python code".  Your question is a bit different.  ;-)

As it happens, if you have a source distribution of a package, you 
can expect to find a PKG-INFO file that contains version info anyway, 
generated from the source file.  This is true for both distutils and 
setuptools-built source distributions.  (It is not the case, alas, 
for simple revision control checkouts.)

Anyway, I was merely addressing the technical question of how to get 
information from the tools that already exist, rather than advocating 
any solutions.

And, along that same line, monkeypatching sys.argv and sys.stdout 
aren't technically necessary for you to get the information from a 
setup script, but a sandbox to keep the setup script from trying to 
do any installation steps is probably a good idea.  (Some people have 
written setup scripts that actually copy files or do other things 
before they even call setup().  Nasty -- and one of the reasons that 
easy_install has a sandboxing facility.)