209 lines
8.2 KiB
Plaintext
209 lines
8.2 KiB
Plaintext
PEP: 411
|
|
Title: Provisional packages in the Python standard library
|
|
Version: $Revision$
|
|
Last-Modified: $Date$
|
|
Author: Nick Coghlan <ncoghlan@gmail.com>,
|
|
Eli Bendersky <eliben@gmail.com>
|
|
Status: Draft
|
|
Type: Informational
|
|
Content-Type: text/x-rst
|
|
Created: 2012-02-10
|
|
Python-Version: 3.3
|
|
Post-History: 2012-02-10
|
|
|
|
|
|
Abstract
|
|
========
|
|
|
|
The process of including a new package into the Python standard library is
|
|
hindered by the API lock-in and promise of backward compatibility implied by
|
|
a package being formally part of Python. This PEP describes a methodology
|
|
for marking a standard library package "provisional" for the period of a single
|
|
minor release. A provisional package may have its API modified prior to
|
|
"graduating" into a "stable" state. On one hand, this state provides the
|
|
package with the benefits of being formally part of the Python distribution.
|
|
On the other hand, the core development team explicitly states that no promises
|
|
are made with regards to the the stability of the package's API, which may
|
|
change for the next release. While it is considered an unlikely outcome,
|
|
such packages may even be removed from the standard library without a
|
|
deprecation period if the concerns regarding their API or maintenance prove
|
|
well-founded.
|
|
|
|
|
|
Proposal - a documented provisional state
|
|
=========================================
|
|
|
|
Whenever the Python core development team decides that a new package should be
|
|
included into the standard library, but isn't entirely sure about whether the
|
|
package's API is optimal, the package can be included and marked as
|
|
"provisional".
|
|
|
|
In the next minor release, the package may either be "graduated" into a normal
|
|
"stable" state in the standard library, remain in provisional state, or be
|
|
rejected and removed entirely from the Python source tree. If the package ends
|
|
up graduating into the stable state after being provisional, its API may
|
|
be changed according to accumulated feedback. The core development team
|
|
explicitly makes no guarantees about API stability and backward compatibility
|
|
of provisional packages.
|
|
|
|
|
|
Marking a package provisional
|
|
-----------------------------
|
|
|
|
A package will be marked provisional by a notice in its documentation page and
|
|
its docstring. The following paragraph will be added as a note at the top of
|
|
the documentation page:
|
|
|
|
The <X> package has been included in the standard library on a
|
|
provisional basis. Backwards incompatible changes (up to and including
|
|
removal of the package) may occur if deemed necessary by the core
|
|
developers.
|
|
|
|
The phrase "provisional basis" will then be a link to the glossary term
|
|
"provisional package", defined as:
|
|
|
|
A provisional package is one which has been deliberately excluded from the
|
|
standard library's normal backwards compatibility guarantees. While major
|
|
changes to such packages are not expected, as long as they are marked
|
|
provisional, backwards incompatible changes (up to and including removal of
|
|
the package) may occur if deemed necessary by core developers. Such changes
|
|
will not be made gratuitously - they will occur only if serious flaws are
|
|
uncovered that were missed prior to the inclusion of the package.
|
|
|
|
This process allows the standard library to continue to evolve over time,
|
|
without locking in problematic design errors for extended periods of time.
|
|
See PEP 411 for more details.
|
|
|
|
The following will be added to the start of the packages's docstring:
|
|
|
|
The API of this package is currently provisional. Refer to the
|
|
documentation for details.
|
|
|
|
Moving a package from the provisional to the stable state simply implies
|
|
removing these notes from its documentation page and docstring.
|
|
|
|
|
|
Which packages should go through the provisional state
|
|
------------------------------------------------------
|
|
|
|
We expect most packages proposed for addition into the Python standard library
|
|
to go through a minor release in the provisional state. There may, however,
|
|
be some exceptions, such as packages that use a pre-defined API (for example
|
|
``lzma``, which generally follows the API of the existing ``bz2`` package),
|
|
or packages with an API that has wide acceptance in the Python development
|
|
community.
|
|
|
|
In any case, packages that are proposed to be added to the standard library,
|
|
whether via the provisional state or directly, must fulfill the acceptance
|
|
conditions set by PEP 2.
|
|
|
|
Criteria for "graduation"
|
|
-------------------------
|
|
|
|
In principle, most provisional packages should eventually graduate to the
|
|
stable standard library. Some reasons for not graduating are:
|
|
|
|
* The package may prove to be unstable or fragile, without sufficient developer
|
|
support to maintain it.
|
|
* A much better alternative package may be found during the preview release.
|
|
|
|
Essentially, the decision will be made by the core developers on a per-case
|
|
basis. The point to emphasize here is that a package's inclusion in the
|
|
standard library as "provisional" in some release does not guarantee it will
|
|
continue being part of Python in the next release.
|
|
|
|
|
|
Rationale
|
|
=========
|
|
|
|
Benefits for the core development team
|
|
--------------------------------------
|
|
|
|
Currently, the core developers are really reluctant to add new interfaces to
|
|
the standard library. This is because as soon as they're published in a
|
|
release, API design mistakes get locked in due to backward compatibility
|
|
concerns.
|
|
|
|
By gating all major API additions through some kind of a provisional mechanism
|
|
for a full release, we get one full release cycle of community feedback
|
|
before we lock in the APIs with our standard backward compatibility guarantee.
|
|
|
|
We can also start integrating provisional packages with the rest of the standard
|
|
library early, so long as we make it clear to packagers that the provisional
|
|
packages should not be considered optional. The only difference between
|
|
provisional APIs and the rest of the standard library is that provisional APIs
|
|
are explicitly exempted from the usual backward compatibility guarantees.
|
|
|
|
Benefits for end users
|
|
----------------------
|
|
|
|
For future end users, the broadest benefit lies in a better "out-of-the-box"
|
|
experience - rather than being told "oh, the standard library tools for task X
|
|
are horrible, download this 3rd party library instead", those superior tools
|
|
are more likely to be just be an import away.
|
|
|
|
For environments where developers are required to conduct due diligence on
|
|
their upstream dependencies (severely harming the cost-effectiveness of, or
|
|
even ruling out entirely, much of the material on PyPI), the key benefit lies
|
|
in ensuring that all packages in the provisional state are clearly under
|
|
python-dev's aegis from at least the following perspectives:
|
|
|
|
* Licensing: Redistributed by the PSF under a Contributor Licensing Agreement.
|
|
* Documentation: The documentation of the package is published and organized via
|
|
the standard Python documentation tools (i.e. ReST source, output generated
|
|
with Sphinx and published on http://docs.python.org).
|
|
* Testing: The package test suites are run on the python.org buildbot fleet
|
|
and results published via http://www.python.org/dev/buildbot.
|
|
* Issue management: Bugs and feature requests are handled on
|
|
http://bugs.python.org
|
|
* Source control: The master repository for the software is published
|
|
on http://hg.python.org.
|
|
|
|
|
|
Candidates for provisional inclusion into the standard library
|
|
==============================================================
|
|
|
|
For Python 3.3, there are a number of clear current candidates:
|
|
|
|
* ``regex`` (http://pypi.python.org/pypi/regex) - approved by Guido [#]_.
|
|
* ``daemon`` (PEP 3143)
|
|
* ``ipaddr`` (PEP 3144)
|
|
|
|
Other possible future use cases include:
|
|
|
|
* Improved HTTP modules (e.g. ``requests``)
|
|
* HTML 5 parsing support (e.g. ``html5lib``)
|
|
* Improved URL/URI/IRI parsing
|
|
* A standard image API (PEP 368)
|
|
* Improved encapsulation of import state (PEP 406)
|
|
* Standard event loop API (PEP 3153)
|
|
* A binary version of WSGI for Python 3 (e.g. PEP 444)
|
|
* Generic function support (e.g. ``simplegeneric``)
|
|
|
|
|
|
Rejected alternatives and variations
|
|
====================================
|
|
|
|
See PEP 408.
|
|
|
|
|
|
References
|
|
==========
|
|
|
|
.. [#] http://mail.python.org/pipermail/python-dev/2012-January/115962.html
|
|
|
|
Copyright
|
|
=========
|
|
|
|
This document has been placed in the public domain.
|
|
|
|
|
|
..
|
|
Local Variables:
|
|
mode: indented-text
|
|
indent-tabs-mode: nil
|
|
sentence-end-double-space: t
|
|
fill-column: 70
|
|
coding: utf-8
|
|
End:
|