[Distutils] get_metadata in Distutils

Phillip J. Eby pje at telecommunity.com
Mon Jan 12 17:07:34 CET 2009

At 02:11 PM 1/12/2009 +0100, Tarek Ziadé wrote:
>Ok, I will introduce in my patch the other formats. I am wondering though, how
>far this would be from an integration of pkg_resources into Distutils/pkgutil,
>with some API on the top and if it makes sense.

It makes sense to me, I just wanted you to be aware how deep a job it 
is.  You're probably going to need a generic function by importer 
type, just like the others in pkgutil.

>The only difference I can see is that I am working on an API that would return
>DistributionMetadata instances

Yep...  which means that you're going to have to reinvent (and 
re-test) a fair number of wheels to get there.  pkg_resources just 
lets you ask for a distribution's PKG-INFO metadata, and get it back 
as a string, regardless of what egg format is in use (including 
distutils).  But to *just* support PKG-INFO, the irony is that you'll 
have to recreate a fair amount of stuff.

>I'd say then : if setutpools version parsing system is superior to

I'm not actually familiar with "versionpredicate", so I couldn't 
say.  It's definitely superior to LooseVersion and StrictVersion, 
which were the only version tools available in the distutils when I 
started all this.

>wouldn't it make sense to merge it into Distutils ?
>Maybe that was the initial plans ?

Yes, and yes.  Setuptools version parsing (and name/version escaping) 
functions at least doesn't have any dependencies on anything 
else.  So that's an easy port.  If you want Requirement objects as 
well (specifying various version ranges), a bit more gets pulled 
in.  However, if all you want is to be able to turn versions into 
opaquely-comparable values, parse_version() and its dependencies are 
all you need.

(By the way, I previously proposed PEP 365 -- that pkg_resources 
simply be bundled in the stdlib -- to address these needs.)

>Well, being able to query the installed version for a package seem to
>me like a feature
>that should live in Distutils or pkgutil
>In the same way, being able to do version arithmetic is rather
>important, and it would be better
>ihmo to have one and only one way to deal with that in Python,
>What are you plans for Setuptools development for the future ?

I hope someday to have some time for it again.  :)

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