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## page was renamed from DebianPythonFAQ
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#pragma section-numbers 2
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This is the FAQ of the debian-python@l.d.o mailing list. It is of particular interest to members of the [[Teams/PythonModulesTeam| Debian Python Modules Team]]. Please also look at [[DebianPython]] for introductory info. This is the FAQ of the debian-python@l.d.o mailing list. It is of particular interest to members of the [[Teams/PythonModulesTeam| Debian Python Modules Team]]. Please also look at [[Python]] for introductory info.
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Debian supports several versions of Python simultaneously. Some packages include modules only for the default version, while others provide modules for all available. Source packages may provide several binary packages for each version of Python or build a single one that suits all. Debian supports several versions of Python simultaneously. Some packages include modules only for the default version, while others provide modules for all available. These are generally all provided within a single binary package, although in the past multiple packages were sometimes used.
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Traditionally, build dependencies for Python extension modules included development packages for all versions of Python they were built for. For compiled modules you still have to specify each dependency separately. For Python-only modules the sole python-dev is sufficient if they use Python-based build system (like the very used distutils), python-support dependency in turn will automagically manage late-bytecompilation. For compiled modules you need to depend on python-all-dev, and python-all-dbg.
For Python-only modules the sole python-all is sufficient if they use Python-based build system (like the very used distutils).
A helper such as dh_python2 (or the deprecated python-support and python-central) will automagically manage bytecompilation.
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As python-support introduce late-bytecompilation, no .pyc/.pyo files shall be shipped in your package. You do no need to spend build time for generating them. With distutils use the "--no-compile -O0" options; if you are using the CDBS class, everything is already done for you. Beware some upstream sources that contain a setup.cfg which override your build options (see [[http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=360848|#360848]]), then you will have to patch it. In all cases, python-support will remove those files if they are generated. As the helpers manage late-bytecompilation, no .pyc/.pyo files shall be shipped in your package. You do no need to spend build time for generating them. With distutils use the "--no-compile -O0" options; dh and the python CDBS classes know how to handle this. Beware some upstream sources that contain a setup.cfg which override your build options (see DebianBug:360848), then you will have to patch it. In all cases, dh_python2 or python-support will remove those files if they are generated.

=== What are dh_python2 and dh_python3? ===

dh_python{2,3} are the python helpers included in the python package since 2.6.6-3.

dh_python2 differs from python-support, in including the per-python-version symlink farm within the binary package, only requiring byte-compilation at install time. Packages using dh_python2 with public modules must be rebuilt when Debian changes the supported Python versions (this should never happen after 2.7).

They can also guess dependencies from requires.txt, for setuptools/distutils packages.

Instructions for transitioning to dh_python2 from [[Python/PythonSupportToDHPython2|python-support]] and [[Python/PyCentral2DhPython2|python-central]].

See [[DebianMan:1/dh_python2|dh_python2(1)]] ([[http://alioth.debian.org/scm/loggerhead/pkg-python/python-defaults-debian/annotate/head:/dh_python2.rst|bzr HEAD]]) or [[DebianMan:1/dh_python3|dh_python3(1)]] for more details.
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Python-support is a tool to handle byte-compilation of python modules when there are several python versions installed on the system. Python-support is a (now deprecated) tool to handle byte-compilation of python modules when there are several python versions installed on the system.
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Package that contains some helper scripts for building and installing python modules independent of the current installed Python version. Python-central is a (now deprecated) package that contains some helper scripts for building and installing python modules independent of the current installed Python version.
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Some information about python-central can be found here:
http://python-modules.alioth.debian.org/python-central_howto.txt
=== Should I use dh_pythonX, python-support or python-central? ===
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=== Should I use python-support or python-central? === dh_python2 is recommended for new Python 2 packages.
dh_python3 is the only helper for Python3.
python-support and python-central are deprecated.
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Most people prefer python-support, because it is better so use that. :)

Some statistics (the number of packages using each method), as of December 16, 2007:
Some statistics (the number of packages using each method - lower number is contrib), as of 2014-04-22:
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~/python-modules$ grep python-support packages/*/trunk/debian/control | wc -l
124
~/python-modules$ grep python-central packages/*/trunk/debian/control | wc -l
62
~$ build-rdeps dh-python | grep total
Found a total of 283 reverse build-depend(s) for dh-python.
Found a total of 2 reverse build-depend(s) for dh-python.
~$ build-rdeps python-support | grep total
Found a total of 4 reverse build-depend(s) for python-support.
Found a total of 585 reverse build-depend(s) for python-support.
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NB! Only python-support numbers are accurate, as other packages may build-depend indirectly on dh-python (for python3) or not use it at all (for python2)
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We don't want to provide ".egg" files within the .deb. However we want to make the "egg meta-information" available so that users can use eggs if they so wish. For that you need to pass the option "--single-version-externally-managed" to the "setup.py install" call. We don't want to provide ".egg" files within the .deb. However we want to make the "egg meta-information" available so that users can use eggs if they so wish. Python >= 2.5 does that by default in distutils. For setuptools based setup.py you need to pass the option "--single-version-externally-managed" to the "setup.py install" call.
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Packages relying on CDBS can do that this way: ==== with dh_python2 ====
This [[http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=652617|bug report]] provides relevant information:

 * Add {{{*.egg-info/*}}} to {{{debian/clean}}}. (This requires Debhelper compatibility >= 7, declared in {{{debian/compat}}}.)
 * Add {{{extend-diff-ignore="^[^/]+\.egg-info/"}}} to debian/source/options. (This requires Debian source package format 3.0, declared in {{{debian/source/format}}}.)

==== with CDBS and setuptools ====
Packages relying on CDBS and setuptools can do that this way:
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=== How do we add Egg support to a package that doesnt support it yet? ===

Basicly, you should modify setup.py to use the setup function of "setuptools" instead of "distutils". Of course, you must then Build-Depends on "python-setuptools (>= 0.6a9)" which is the first version supporting the egg-info directories.

Check the following links for documentation about setuptools and creation of Eggs:
 * http://peak.telecommunity.com/DevCenter/setuptools
 * http://peak.telecommunity.com/DevCenter/PythonEggs#building-eggs

Example of minimal patch:
{{{
--- elementtree-1.2.6.old/setup.py 2006-04-18 12:25:33.000000000 +0000
+++ elementtree-1.2.6/setup.py 2006-04-18 12:26:30.000000000 +0000
@@ -7,6 +7,7 @@
 #

 from distutils.core import setup
+from setuptools import setup

 try:
     # add download_url syntax to distutils
}}}

Adding "egg support" is only required in some specific cases: when another software uses the python module via an egg and when this egg support is not yet integrated upstream.

Debian Python FAQ

This is the FAQ of the debian-python@l.d.o mailing list. It is of particular interest to members of the Debian Python Modules Team. Please also look at Python for introductory info.

1. What are the projects and documentation available ?

If you're interested in help packaging Python itself, there's pkg-python but if you want to help with the Python modules or packaging a new one, you should look at Debian Python Modules Team project. Both groups discuss its activities in the same debian-python@l.d.o mailing list.

1.1. python-modules

The Debian Python Modules Team has its own policy, but keep in mind that they follow Debian Python Policy and of course Debian Policy too.

2. Multiple python versions support

Debian supports several versions of Python simultaneously. Some packages include modules only for the default version, while others provide modules for all available. These are generally all provided within a single binary package, although in the past multiple packages were sometimes used.

The general trend is to reduce that diversity and provide modules for all Python versions available within Debian using the following guidelines.

2.1. Build dependencies

For compiled modules you need to depend on python-all-dev, and python-all-dbg. For Python-only modules the sole python-all is sufficient if they use Python-based build system (like the very used distutils). A helper such as dh_python2 (or the deprecated python-support and python-central) will automagically manage bytecompilation.

3. Note on bytecompilation for pure Python modules

As the helpers manage late-bytecompilation, no .pyc/.pyo files shall be shipped in your package. You do no need to spend build time for generating them. With distutils use the "--no-compile -O0" options; dh and the python CDBS classes know how to handle this. Beware some upstream sources that contain a setup.cfg which override your build options (see 360848), then you will have to patch it. In all cases, dh_python2 or python-support will remove those files if they are generated.

3.1. What are dh_python2 and dh_python3?

dh_python{2,3} are the python helpers included in the python package since 2.6.6-3.

dh_python2 differs from python-support, in including the per-python-version symlink farm within the binary package, only requiring byte-compilation at install time. Packages using dh_python2 with public modules must be rebuilt when Debian changes the supported Python versions (this should never happen after 2.7).

They can also guess dependencies from requires.txt, for setuptools/distutils packages.

Instructions for transitioning to dh_python2 from python-support and python-central.

See dh_python2(1) (bzr HEAD) or dh_python3(1) for more details.

3.2. What is python-support?

Python-support is a (now deprecated) tool to handle byte-compilation of python modules when there are several python versions installed on the system.

See /usr/share/doc/python-support/README.gz or SVN README for up-to-date information.

3.3. What is python-central?

Python-central is a (now deprecated) package that contains some helper scripts for building and installing python modules independent of the current installed Python version.

3.4. Should I use dh_pythonX, python-support or python-central?

dh_python2 is recommended for new Python 2 packages. dh_python3 is the only helper for Python3. python-support and python-central are deprecated.

Some statistics (the number of packages using each method - lower number is contrib), as of 2014-04-22:

~$ build-rdeps dh-python | grep total
Found a total of 283 reverse build-depend(s) for dh-python.
Found a total of 2 reverse build-depend(s) for dh-python.
~$ build-rdeps python-support | grep total
Found a total of 4 reverse build-depend(s) for python-support.
Found a total of 585 reverse build-depend(s) for python-support.

NB! Only python-support numbers are accurate, as other packages may build-depend indirectly on dh-python (for python3) or not use it at all (for python2)

4. Python eggs

4.1. What are Python eggs?

http://peak.telecommunity.com/DevCenter/PythonEggs

4.2. How should we package Python eggs?

We don't want to provide ".egg" files within the .deb. However we want to make the "egg meta-information" available so that users can use eggs if they so wish. Python >= 2.5 does that by default in distutils. For setuptools based setup.py you need to pass the option "--single-version-externally-managed" to the "setup.py install" call.

4.2.1. with dh_python2

This bug report provides relevant information:

  • Add *.egg-info/* to debian/clean. (This requires Debhelper compatibility >= 7, declared in debian/compat.)

  • Add extend-diff-ignore="^[^/]+\.egg-info/" to debian/source/options. (This requires Debian source package format 3.0, declared in debian/source/format.)

4.2.2. with CDBS and setuptools

Packages relying on CDBS and setuptools can do that this way:

# Install egg-info directories
DEB_PYTHON_INSTALL_ARGS_ALL += --single-version-externally-managed


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