[Python-Dev] Keyword meanings [was: Accept just PEP-0426]

Donald Stufft donald.stufft at gmail.com
Thu Dec 6 12:33:42 CET 2012

On Thursday, December 6, 2012 at 6:28 AM, Vinay Sajip wrote:
> Donald Stufft <donald.stufft <at> gmail.com (http://gmail.com)> writes:
> Never mind the "Obsoletes" information - even the more useful "Requires-Dist"
> information is not exposed via PyPI, even though it appears to be stored in the
> database. (Or if it is, please point me to where - I must have missed it.)

Requires-Dist doesn't exist for more than a handful of packages. But PyPI exposes
it via the XMLRPC API, possibly the JSON api as well. 
> Even if this were to be made available, it's presumably obtained from PKG-INFO.
> As I understand, this data is not considered reliable - for example, pip runs
> egg_info on downloaded packages to get updated information when determining
> dependencies to be downloaded. If the Requires-Dist info in PKG-INFO can't be
> relied on, surely less critical information such as Obsoletes can't be relied on,
> either?

pip runs egg_info because setuptools does not write out to PKG-INFO what
the dependencies are (it does write it out to a different text file though). But IIRC
that text file is not guaranteed to exist in the distribution. There's also the
history where pip was trying to preserve as much backwards compat with
easy_install as it could, and if you used the file that egg_info writes out
then you'll only get the requirements for the system that the distribution was
packaged on. Any if statements that affect the dependencies won't be
in effect.
> Regards,
> Vinay Sajip
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