[Python-checkins] peps: PEP 453 updates
nick.coghlan
python-checkins at python.org
Sun Sep 22 07:57:57 CEST 2013
http://hg.python.org/peps/rev/b2993450b32a
changeset: 5140:b2993450b32a
user: Nick Coghlan <ncoghlan at gmail.com>
date: Sun Sep 22 15:57:28 2013 +1000
summary:
PEP 453 updates
- use the module name Antoine suggested
- list the five distinct parts of the proposal when
describing the implementation strategy
- note the bootstrap approach makes it easy to let people opt-out
- allow distros to redirect a global ensurepip invocation to the
system package manager
- decide the open questions in favour of the currently documented
approaches (i.e. no changes to uninstallation, update the
directory layout and PATH handling on Windows)
files:
pep-0453.txt | 140 +++++++++++++++++++++++---------------
1 files changed, 83 insertions(+), 57 deletions(-)
diff --git a/pep-0453.txt b/pep-0453.txt
--- a/pep-0453.txt
+++ b/pep-0453.txt
@@ -34,7 +34,7 @@
Proposal
========
-This PEP proposes the inclusion of an ``extractpip`` bootstrapping module in
+This PEP proposes the inclusion of an ``ensurepip`` bootstrapping module in
Python 3.4, as well as in the next maintenance releases of Python 3.3 and
2.7.
@@ -164,11 +164,11 @@
Explicit bootstrapping mechanism
================================
-An additional module called ``extractpip`` will be added to the standard
+An additional module called ``ensurepip`` will be added to the standard
library whose purpose is to install pip and any of its dependencies into the
appropriate location (most commonly site-packages). It will expose a
callable named ``bootstrap()`` as well as offer direct execution via
-``python -m extractpip``.
+``python -m ensurepip``.
The bootstrap will *not* contact PyPI, but instead rely on a private copy
of pip stored inside the standard library. Accordingly, only options
@@ -208,15 +208,15 @@
-----------------------
To ensure there is no need for network access when installing Python or
-creating virtual environments, the ``extractpip`` module will, as an
+creating virtual environments, the ``ensurepip`` module will, as an
implementation detail, include a complete private copy of pip and its
dependencies which will be used to extract pip and install it into the target
environment. It is important to stress that this private copy of pip is
*only* an implementation detail and it should *not* be relied on or
assumed to exist beyond the public capabilities exposed through the
-``extractpip`` module (and indirectly through ``venv``).
+``ensurepip`` module (and indirectly through ``venv``).
-There is not yet a reference ``extractpip`` implementation. The existing
+There is not yet a reference ``ensurepip`` implementation. The existing
``get-pip.py`` bootstrap script demonstrates an earlier variation of the
general concept, but the standard library version would take advantage of
the improved distribution capabilities offered by the CPython installers
@@ -225,11 +225,28 @@
contact PyPI (instead installing directly from the private wheel files.
Rather than including separate code to handle the bootstrapping, the
-``extractpip`` module will manipulate sys.path appropriately to allow
+``ensurepip`` module will manipulate sys.path appropriately to allow
the wheel files to be used to install themselves, either into the current
Python installation or into a virtual environment (as determined by the
options passed to the bootstrap command).
+It is proposed that the implementation be carried out in five separate
+steps (all steps after the first are independent of each other and can be
+carried out in any order):
+
+* the first step would add the ``ensurepip`` module and the private copies
+ of the most recently released versions of pip and setuptools, and update
+ the "Installing Python Modules" documentation. This change
+ would be applied to Python 2.7, 3.3 and 3.4.
+* the Windows installer would be updated to offer the new ``pip``
+ installation option for Python 2.7.6, 3.3.3 and 3.4.0.
+* the Mac OS X installer would be updated to offer the new ``pip``
+ installation option for Python 2.7.6, 3.3.3 and 3.4.0.
+* the ``venv`` module and ``pyvenv`` command would be updated to make use
+ of ``ensurepip`` in Python 3.4+
+* the PATH handling and ``sysconfig`` directory layout on Windows would be
+ updated for Python 3.4+
+
Proposed CLI
------------
@@ -238,7 +255,7 @@
options::
Usage:
- python -m extractpip [options]
+ python -m ensurepip [options]
General Options:
-h, --help Show help.
@@ -256,14 +273,13 @@
creating a virtual environment.
Users that want to retrieve the latest version from PyPI, or otherwise
-needing more flexibility, should invoke the extracted ``pip``
-appropriately.
+need more flexibility, should invoke the extracted ``pip`` appropriately.
Proposed module API
-------------------
-The proposed ``extractpip`` module API consists of the following two
+The proposed ``ensurepip`` module API consists of the following two
functions::
def version():
@@ -290,12 +306,12 @@
If the option is checked, then the installer will invoke the following
command with the just installed Python::
- python -m extractpip --upgrade
+ python -m ensurepip --upgrade
This ensures that, by default, installing or updating CPython will ensure
that the installed version of pip is at least as recent as the one included
with that version of CPython. If a newer version of pip has already been
-installed then ``python -m extractpip --upgrade`` will simply return without
+installed then ``python -m ensurepip --upgrade`` will simply return without
doing anything.
@@ -303,11 +319,11 @@
----------------------
While the prebuilt binary installers will be updated to run
-``python -m extractpip`` by default, no such change will be made to the
+``python -m ensurepip`` by default, no such change will be made to the
``make install`` and ``make altinstall`` commands of the source
distribution.
-``extractpip`` itself (including the private copy of ``pip`` and its
+``ensurepip`` itself (including the private copy of ``pip`` and its
dependencies) will still be installed normally (as it is a regular
part of the standard library), only the implicit installation of pip and
its dependencies will be skipped.
@@ -315,7 +331,7 @@
Keeping the pip bootstrapping as a separate step for ``make``-based
installations should minimize the changes CPython redistributors need to
make to their build processes. Avoiding the layer of indirection through
-``make`` for the ``extractpip`` invocation avoids any challenges
+``make`` for the ``ensurepip`` invocation avoids any challenges
associated with determining where to install the extracted ``pip``.
@@ -372,7 +388,7 @@
Bundling CA certificates with CPython
-------------------------------------
-The ``extractpip`` implementation will include the ``pip`` CA bundle along
+The ``ensurepip`` implementation will include the ``pip`` CA bundle along
with the rest of ``pip``. This means CPython effectively includes
a CA bundle that is used solely by ``pip`` after it has been extracted.
@@ -392,8 +408,8 @@
when Python 3.4.0 is released).
This PEP proposes that, if pip still requires it as a dependency,
-``extractpip`` will include a private copy of ``setuptools`` (in addition
-to the private copy of ``extractpip``). ``python -m extractpip`` will then
+``ensurepip`` will include a private copy of ``setuptools`` (in addition
+to the private copy of ``ensurepip``). ``python -m ensurepip`` will then
install the private copy in addition to installing ``pip`` itself.
However, this behavior is officially considered an implementation
@@ -403,14 +419,14 @@
Once pip is able to run ``pip install --upgrade pip`` without needing
``setuptools`` installed first, then the private copy of ``setuptools``
-will be removed from ``extractpip`` in subsequent CPython releases.
+will be removed from ``ensurepip`` in subsequent CPython releases.
Updating the private copy of pip
--------------------------------
In order to keep up with evolutions in packaging as well as providing users
-with as recent version a possible the ``extractpip`` module will be
+with as recent version a possible the ``ensurepip`` module will be
regularly updated to the latest versions of everything it bootstraps.
After each new ``pip`` release, and again during the preparation for any
@@ -419,10 +435,10 @@
source repository have been updated to the latest versions.
-Updating the extractpip module API and CLI
-------------------------------------------
+Updating the ensurepip module API and CLI
+-----------------------------------------
-Like ``venv`` and ``pyvenv``, the ``extractpip`` module API and CLI
+Like ``venv`` and ``pyvenv``, the ``ensurepip`` module API and CLI
will be governed by the normal rules for the standard library: no
new features are permitted in maintenance releases.
@@ -450,10 +466,10 @@
released.
-Open Question: Uninstallation
-=============================
+Uninstallation
+==============
-No changes are currently proposed to the uninstallation process. The
+No changes are proposed to the uninstallation process by this PEP. The
bootstrapped pip will be installed the same way as any other pip
installed packages, and will be handled in the same way as any other
post-install additions to the Python environment.
@@ -462,20 +478,13 @@
left behind after uninstallation, since those files won't be associated
with the Python MSI installer.
-.. note::
+While the case can be made for the CPython installers clearing out these
+directories automatically, changing that behaviour is considered outside
+the scope of this PEP.
- Perhaps the installer should be updated to clobber everything in
- site-packages and the Scripts directory when uninstalled (treating them
- as "data directories" from Python's point of view), but I would prefer
- not to make this PEP conditional on that change.
-
-Open Question: Script Execution on Windows
-==========================================
-
-.. note::
-
- Perhaps this question should be separated out from the PEP?
+Script Execution on Windows
+===========================
While the Windows installer was updated in Python 3.3 to optionally
make ``python`` available on the PATH, no such change was made to
@@ -539,7 +548,9 @@
installing the separate pip package when a user executes ``pip`` without
it being installed. Systems that choose this option should ensure that
the ``pyvenv`` command still installs pip into the virtual environment
- by default.
+ by default, but may modify the ``ensurepip`` module in the system Python
+ installation to redirect to the platform provided mechanism when
+ installing ``pip`` globally.
* Do not remove the bundled copy of pip.
@@ -549,8 +560,8 @@
downstream distributors have already made exception to the common
"debundling" policy.
* This does mean that if ``pip`` needs to be updated due to a security
- issue, so does the bundled version in the ``extractpip`` bootstrap module
- * However, altering the bundled version of pip to remove the embedded
+ issue, so does the private copy in the ``ensurepip`` bootstrap module
+ * However, altering the private copy of pip to remove the embedded
CA certificate bundle and rely on the system CA bundle instead is a
reasonable change.
@@ -564,14 +575,13 @@
made to the redistributed version of Python.
* Checking the version of pip that will be bootstrapped using
- ``python -m extractpip --version`` or ``extractpip.version()``.
- * Installation of the bundled version of pip into a global or virtual
- python environment using ``python -m extractpip`` or
- ``extractpip.bootstrap()``.
+ ``python -m ensurepip --version`` or ``ensurepip.version()``.
+ * Installation of pip into a global or virtual python environment using
+ ``python -m ensurepip`` or ``ensurepip.bootstrap()``.
* ``pip install --upgrade pip`` in a global installation should not affect
any already created virtual environments (but is permitted to affect
- future virtual environments, even though it will not do so in the
- normal case).
+ future virtual environments, even though it will not do so when using
+ the upstream version of ``ensurepip``).
* ``pip install --upgrade pip`` in a virtual environment should not affect
the global installation.
@@ -602,7 +612,7 @@
Backwards Compatibility
-----------------------
-The public API and CLI of the ``extractpip`` module itself will fall under
+The public API and CLI of the ``ensurepip`` module itself will fall under
the typical backwards compatibility policy of Python for its standard
library. The externally developed software that this PEP bundles does not.
@@ -614,7 +624,7 @@
Security Releases
-----------------
-Any security update that affects the ``extractpip`` module will be shared
+Any security update that affects the ``ensurepip`` module will be shared
prior to release with the Python Security Response Team
(security at python.org). The PSRT will then decide if the reported issue
warrants a security release of CPython with an updated private copy of
@@ -692,13 +702,18 @@
including complete public copies of third-party projects in the standard
library.
-Finally, the approach described in this PEP avoids some technical issues
-related to handle CPython maintenance updates when pip has been independently
-updated to a more recent version. The proposed pip-based bootstrapping
-mechanism handles that automatically, since pip and the system installer
-never get into a fight about who owns the pip installation (it is always
-managed through pip, either directly, or indirectly via the getpip bootstrap
-module).
+The approach described in this PEP also avoids some technical issues
+related to handling CPython maintenance updates when pip has been
+independently updated to a more recent version. The proposed pip-based
+bootstrapping mechanism handles that automatically, since pip and the
+system installer never get into a fight about who owns the pip
+installation (it is always managed through pip, either directly, or
+indirectly via the ``ensurepip`` bootstrap module).
+
+Finally, the separate bootstrapping step means it also easy to avoid
+installing ``pip`` at all if end users so desire. This is often the case
+if integrators are using system packages to handle installation of
+components written in multiple languages using a common set of tools.
Defaulting to --user installation
@@ -727,6 +742,17 @@
.. [#homebrew] `Homebrew <http://brew.sh/>`
.. [#conda] `Conda <http://www.continuum.io/blog/conda>`
+.. [1] Discussion thread 1 (distutils-sig)
+ (https://mail.python.org/pipermail/distutils-sig/2013-August/022529.html)
+
+.. [2] Discussion thread 2 (distutils-sig)
+ (https://mail.python.org/pipermail/distutils-sig/2013-September/022702.html)
+
+.. [3] Discussion thread 3 (python-dev)
+ (https://mail.python.org/pipermail/python-dev/2013-September/128723.html)
+
+.. [4] Discussion thread 4 (python-dev)
+ (https://mail.python.org/pipermail/python-dev/2013-September/128780.html)
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Repository URL: http://hg.python.org/peps
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