[Python-ideas] PEP: Distributing a Subset of the Standard Library

[Nick Coghlan]

On 7 December 2016 at 02:50, Tomas Orsava <torsava at redhat.com> wrote:
> So using _sysconfigdata as inspiration, it would likely be possible to
> provide a "sysconfig.get_missing_modules()" API that the default
> sys.excepthook() could use to report that a particular import didn't
> work because an optional standard library module hadn't been built.
>
> Quite interesting. And sysconfig.get_missing_modules() wouldn't even have to
> be generated during the build process, because it would be called only when
> the import has failed, at which point it is obvious Python was built without
> said component (like _sqlite3). So do you see that as an acceptable
> solution?

Oh, I'd missed that - yes, the sysconfig API could potentially be
something like `sysconfig.get_stdlib_modules()` and
`sysconfig.get_optional_modules()` instead of specifically reporting
which ones were missed by the build process. There'd still be some
work around generating the manifests backing those APIs at build time
(including getting them right for Windows as well), but it would make
some other questions that are currently annoying to answer relatively
straightforward (see
http://stackoverflow.com/questions/6463918/how-can-i-get-a-list-of-all-the-python-standard-library-modules
for more on that)

> Do you prefer the one you suggested previously?

The only strong preference I have around how this is implemented is
that I don't want to add complex single-purpose runtime infrastructure
for the task. For all of the other specifics, I think it makes sense
to err on the side of "What will be easiest to maintain over time?"

> Alternatively, can the contents of site.py be generated during the build
> process? Because if some modules couldn't be built, a custom implementation
> of sys.excepthook might be generated there with the data for the modules
> that failed to be built.

We don't really want site.py itself to be auto-generated (although it
could be updated to use Argument Clinic selectively if we deemed that
to be an appropriate thing to do), but there's no problem with
generating either data modules or normal importable modules that get
accessed from site.py.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia