[Python-ideas] Defining an easily installable "Recommended baseline package set"

Guido van Rossum guido at python.org
Sun Oct 29 01:16:39 EDT 2017

Why? What's wrong with pip install? Why complicate things? Your motivation
is really weak here. "beneficial"? "difficult cases"?

On Sat, Oct 28, 2017 at 8:57 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> Over on python-dev, the question of recommending MRAB's "regex" module
> over the standard library's "re" module for more advanced regular
> expressions recently came up again.
> Because of various logistical issues and backwards compatibility risks,
> it's highly unlikely that we'll ever be able to swap out the current _sre
> based re module implementation in the standard library for an
> implementation based on the regex module.
> At the same time, it would be beneficial to have a way to offer an even
> stronger recommendation to redistributors that we think full-featured
> general purpose Python scripting environments should offer the regex module
> as an opt-in alternative to the baseline re feature set, since that would
> also help with other currently difficult cases like the requests module.
> What I'm thinking is that we could make some relatively simple additions
> to the `ensurepip` and `venv` modules to help with this:
> 1. Add a ensurepip.RECOMMENDED_PACKAGES mapping keyed by standard library
> module names containing dependency specifiers for recommended third party
> packages for particular tasks (e.g. "regex" as an enhanced alternative to
> "re", "requests" as an enhanced HTTPS-centric alternative to
> "urllib.request")
> 2. Add a new `install_recommended` boolean flag to ensurepip.bootstrap
> 3. Add a corresponding `--install-recommended flag to the `python -m
> ensurepip` CLI
> 4. Add a corresponding `--install-recommended flag to the `python -m venv`
> CLI (when combined with `--without-pip`, this would run pip directly from
> the bundled wheel file to do the installations)
> We'd also need either a new informational PEP or else a section in the
> developer guide to say that the contents of `ensurepip.RECOMMENDED_PACKAGES`
> are up to the individual module maintainers (hence keying the mapping by
> standard library module name, rather than having a single flat list for the
> entire standard library).
> For redistributors with weak dependency support, these reference
> interpreter level recommendations could become redistributor level
> recommendations. Redistributors without weak dependency support could still
> make a distinction between "default" installations (which would include
> them) and "minimal" installations (which would exclude them).
> Folks writing scripts and example code for independent distribution (i.e.
> no explicitly declared dependencies) could then choose between relying on
> just the standard library (as now), or on the standard library plus
> independently versioned recommended packages.
> Cheers,
> Nick.
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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--Guido van Rossum (python.org/~guido)
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