Revision as of 21:27, 29 October 2009

Packaging Python modules for Python 3

I hope to add a parallel-installable Python 3 stack to Fedora 13.

See the feature page: https://fedoraproject.org/wiki/Features/Python3F13 and also this thread: https://www.redhat.com/archives/fedora-devel-list/2009-October/msg00054.html

This requires us to come up with a sane way to package Python 3 modules, and this requires us to generalize our python packaging rules to support more than one python runtime.

The existing Python packaging guidelines are here: Packaging/Python

Runtimes

There will be multiple python runtimes, one for each supported major/minor release combination.

Each runtime corresponds to a binary of the form /usr/bin/python$MAJOR.$MINOR

One of these python runtimes is the "system runtime". It can be identified by the destination of the symlink /usr/bin/python

The output of "rpm -q --provides" of each runtime rpm MUST contain a line of the form:

 Provides: python(abi) = $MAJOR-$MINOR

For example, a python-3.1 runtime rpm should have this output:

 Provides: python(abi) = 3.1

Similarly, python modules using these runtimes should have a corresponding "Requires" line.

Naming

(to be written)

Current python package naming guidelines are here: Packaging/NamingGuidelines#Addon_Packages_.28python_modules.29

Layout

Proposed rule: All files with an extension of .py/.pyo/.pyc MUST be either

within a runtime package, and below /usr/lib/python$MAJOR-$MINOR for that runtime, or
for a specific runtime package, and below /usr/lib/python$MAJOR-$MINOR/site-packages for that runtime, or
for the system python runtime.

For example, python code for the 3.1 runtime needs to be below /usr/lib/python3.1/site-packages

.pyo/.pyc files

Compiled .pyo/.pyc files embed a magic number, indicating which python version they are for; python libraries have a corresponding magic number.

Proposed rule: All .pyo/.pyc files below /usr/lib/python$MAJOR.$MINOR MUST have a magic number corresponding to that for /usr/bin/python$MAJOR.$MINOR

Thus e.g. /usr/lib/python2.6/site-packages/libxml2.pyc must have the same magic number as that of /usr/bin/python2.6

Similarly, /usr/lib/python3.1/site-packages/libxml2.pyc must have the same magic number as that of /usr/bin/python3.1

TODO: write an rpmlint test for this. See initial work here: https://www.zarb.org/pipermail/rpmlint-discuss/2009-October/000775.html and here: http://dmalcolm.fedorapeople.org/rpmlint/add-tests-for-python-bytecode-files.patch

@@ Line 17: / Line 17: @@
 The output of "rpm -q --provides" of each runtime rpm '''MUST''' contain a line of the form:
-   Provides: python-abi-$MAJOR-$MINOR-$MAGIC
+   Provides: python(abi) = $MAJOR-$MINOR
-For example, a python-2.7 runtime rpm with ABI 62171 should have this output:
+For example, a python-3.1 runtime rpm should have this output:
-   Provides: python-abi-2.7-62171
+   Provides: python(abi) = 3.1
-and another with ABI 62181 should have this output:
-  Provides: python-abi-2.7-62181
-(this is a change from current guidelines, to allow for different runtimes to be installable in parallel, and allowing for multiple magic numbers)
+Similarly, python modules using these runtimes should have a corresponding "Requires" line.
 == Naming ==

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