[Python-Dev] Fwd: PEP 426 is now the draft spec for distribution metadata 2.0

M.-A. Lemburg mal at egenix.com
Tue Feb 19 14:23:55 CET 2013

On 19.02.2013 11:28, Nick Coghlan wrote:
> On Tue, Feb 19, 2013 at 7:37 PM, M.-A. Lemburg <mal at egenix.com> wrote:
>> On 17.02.2013 11:11, Nick Coghlan wrote:
>> I'm not against modernizing the format, but given that version 1.2
>> has been out for around 8 years now, without much following,
>> I think we need to make the implementation bit a requirement
>> before accepting the PEP.
> It is being implemented in distlib, and the (short!) appendix to the
> PEP itself shows how to read the format using the standard library's
> email module.

Hmm, what is distlib and where does it live ?

The PEP only shows how to parse the RFC822-style format used by the
metadata. That's not what I was referring to.

If a tools wants to support metadata 2.0, it has to support all
the complicated stuff as well, i.e. handle the requires fields,
the environment markers and version comparisons/sorting.

> v2.0 is designed to fix many of the issues that prevented the adoption
> of v1.2, including tweaks to the standardised version scheme and the
> addition of a formal extension mechanism to avoid the ad hoc
> extensions that occurred with earlier metadata versions.

Some more notes:

* I find it confusing that we now have two version schemes,
  one defined in PEP 426 (hidden in the middle of the document)
  and one in PEP 386. It would be better to amend or replace
  PEP 386, since that's where you look for Python version strings.

* PEP 426 doesn't include any mention of the egg distribution format,
  even though it's the most popular distribution format at the moment.
  It should at least include the location of the metadata file
  in eggs (EGG-INFO/PKG-INFO) and egg installations

Not sure whether related or not, I also think it would be a good idea
to make the metadata file available on PyPI for download (could be sent
there when registering the package release). The register command
only posts the data as 1.0 metadata, but includes fields from
metadata 1.1. PyPI itself only displays part of the data.

It would be useful to have the metadata readily available for
inspection on PyPI without having to download one of the
distribution files first.

Marc-Andre Lemburg

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