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 <section id="abstract">
<h1>Abstract<a class="headerlink" href="#abstract" title="Permalink to this headline">¶</a></h1>
This document describes the packaging of Python within the Debian
GNU/Linux distribution and the policy requirements for packaged Python
programs and modules.
</section>
<section id="contents">
<h1>Contents<a class="headerlink" href="#contents" title="Permalink to this headline">¶</a></h1>
<div class="toctree-wrapper compound">
<section id="copyright">
<h2>1. Copyright<a class="headerlink" href="#copyright" title="Permalink to this headline">¶</a></h2>
1999-2021, Software in the Public Interest
<dl class="simple">
<dt>Authors:</dt><dd><ul class="simple">
<li>Neil Schemenauer &lt;<a class="reference external" href="mailto:nas&#37;&#52;&#48;debian&#46;org">nas&#64;debian&#46;org</a>&gt;</li>
<li>Matthias Klose &lt;<a class="reference external" href="mailto:doko&#37;&#52;&#48;debian&#46;org">doko&#64;debian&#46;org</a>&gt;</li>
<li>Gregor Hoffleit &lt;<a class="reference external" href="mailto:flight&#37;&#52;&#48;debian&#46;org">flight&#64;debian&#46;org</a>&gt;</li>
<li>Josselin Mouette &lt;<a class="reference external" href="mailto:joss&#37;&#52;&#48;debian&#46;org">joss&#64;debian&#46;org</a>&gt;</li>
<li>Joe Wreschnig &lt;<a class="reference external" href="mailto:piman&#37;&#52;&#48;debian&#46;org">piman&#64;debian&#46;org</a>&gt;</li>
<li>Loïc Minier &lt;<a class="reference external" href="mailto:lool&#37;&#52;&#48;debian&#46;org">lool&#64;debian&#46;org</a>&gt;</li>
<li>Scott Kitterman &lt;<a class="reference external" href="mailto:scott&#37;&#52;&#48;kitterman&#46;com">scott&#64;kitterman&#46;com</a>&gt;</li>
<li>Barry Warsaw &lt;<a class="reference external" href="mailto:barry&#37;&#52;&#48;debian&#46;org">barry&#64;debian&#46;org</a>&gt;</li>
<li>Ben Finney &lt;<a class="reference external" href="mailto:ben+debian&#37;&#52;&#48;benfinney&#46;id&#46;au">ben+debian&#64;benfinney&#46;id&#46;au</a>&gt;</li>
<li>Neil Williams &lt;<a class="reference external" href="mailto:codehelp&#37;&#52;&#48;debian&#46;org">codehelp&#64;debian&#46;org</a>&gt;</li>
<li>Stefano Rivera &lt;<a class="reference external" href="mailto:stefanor&#37;&#52;&#48;debian&#46;org">stefanor&#64;debian&#46;org</a>&gt;</li>
</ul>
</dd>
</dl>
This manual is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
A copy of the GNU General Public License version 2 is available as
<code class="file docutils literal notranslate">/usr/share/common-licences/GPL-2</code> in the Debian GNU/Linux system,
or on the World Wide Web at <a class="reference external" href="https://www.gnu.org/licenses/old-licenses/gpl-2.0.html">GNU General Public License, version 2</a>.
You can also obtain it by writing to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
</section>
<section id="completing-the-move-to-python-3">
<h2>2. Completing the move to Python 3<a class="headerlink" href="#completing-the-move-to-python-3" title="Permalink to this headline">¶</a></h2>
Debian has previously supported two Python stacks, one for Python 3 and
one for Python 2.
The goal for Debian is to reduce this to one stack, dropping the Python
2 stack and interpreter for the Bullseye release.
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0404">PEP 404</a> states that no more major Python 2 releases are planned,
although the latest released minor version 2.7 will see some extended
support, documented in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0466">PEP 466</a>.
Packages in Debian should use Python 3.
New packages must use Python 3 from the initial upload, new upstream
versions for existing packages must use Python 3.
If Python 2 is still supported in Bullseye, selected packages may
continue using Python 2 until Python 3 support is available for those
packages.
Please discuss all use of Python 2 on the debian-python mailing list
before uploading.
<ol class="arabic simple">
<li>Applications should use Python 3 and must not be packaged for Python
2 as well.
If an application supports only Python 2, the application may need
to be removed from Debian so that it does not block removal of other
Python 2 packages.</li>
<li>Python libraries need to support Python 3 and new versions must be
packaged for Python 3.
Existing Python 2 libraries must not be dropped before the last
reverse dependency is removed.
New Python 2 libraries must not be introduced.</li>
<li>Python 3 should be used for the packaging if the packaging scripts
use Python.</li>
</ol>
<section id="removal-of-the-unversioned-packages">
<h3>2.1. Removal of the unversioned packages<a class="headerlink" href="#removal-of-the-unversioned-packages" title="Permalink to this headline">¶</a></h3>
Starting with the Debian 11 release (bullseye), the binary packages
<code class="docutils literal notranslate">python</code>, <code class="docutils literal notranslate">python-minimal</code>, <code class="docutils literal notranslate">python-dev</code>, <code class="docutils literal notranslate">python-dbg</code> and
<code class="docutils literal notranslate">python-doc</code> are removed. No package in the archive must use any of
these packages as build dependencies, dependencies, recommendations or
suggestions.
</section>
<section id="unversioned-python-commands">
<h3>2.2. Unversioned python commands<a class="headerlink" href="#unversioned-python-commands" title="Permalink to this headline">¶</a></h3>
For the Debian 11 release (bullseye), the <code class="file docutils literal notranslate">/usr/bin/python</code>
command is provided in the <code class="docutils literal notranslate">python-is-python2</code> package (pointing to
<code class="file docutils literal notranslate">/usr/bin/python2</code>). The <code class="file docutils literal notranslate">/usr/bin/python-config</code> and
<code class="file docutils literal notranslate">/usr/bin/pydoc</code> commands are provided in the
<code class="docutils literal notranslate">python-dev-is-python2</code> package. These package are not installed by
default for new installations, but only for upgrades from the Debian
10 release (buster). These packages should be removed after an
upgrade. These packages will not be part of the Debian 12 release
(bookworm).
The packages <code class="docutils literal notranslate">python-is-python3</code> and <code class="docutils literal notranslate">python-dev-is-python3</code>
provide the <code class="file docutils literal notranslate">/usr/bin/python</code>, <code class="file docutils literal notranslate">/usr/bin/python-config</code>
and <code class="file docutils literal notranslate">/usr/bin/pydoc</code> commands pointing to Python3. These
packages can be installed by developers and users to use the
unversioned commands. NOTE: Locally installed software not yet ported
to Python3 is likely to break when installing these packages.
The packages <code class="docutils literal notranslate">python-is-python3</code>, <code class="docutils literal notranslate">python-dev-is-python3</code>,
<code class="docutils literal notranslate">python-is-python2</code> and <code class="docutils literal notranslate">python-dev-is-python2</code> must not be used
as build dependencies, dependencies, recommendations or suggestions.
</section>
</section>
<section id="python-packaging">
<h2>3. Python Packaging<a class="headerlink" href="#python-packaging" title="Permalink to this headline">¶</a></h2>
<section id="versions">
<h3>3.1. Versions<a class="headerlink" href="#versions" title="Permalink to this headline">¶</a></h3>
At any given time, the binary package <code class="docutils literal notranslate">python3</code> will represent the
current default Debian Python 3 version; the binary package <code class="docutils literal notranslate">python</code>
will represent the current default Debian Python 2 version, for as long
as it exists.
As far as is reasonable, Python 3 and Python 2 should be treated as
separate runtime systems with minimal interdependencies.
In some cases, Python policy explicitly references Python helper tools.
For Debian Stretch, the <code class="docutils literal notranslate">dh-python</code> package provides the only such
tools; earlier helpers have been removed from Debian.
It is a design goal to fully specify required interfaces and functions
in policy for Python 3 and to avoid enshrining specific implementation
details in policy.
Except as noted, policy for Python 2 is the same as Python 3 with the
exception of the different major version number as needed to distinguish
them.
The default Debian Python version, for each of Python 3 and Python 2,
should always be the latest stable upstream version that can be fully
integrated in Debian.
There may be newer supported or unsupported versions included in Debian
if they are not fully integrated for a particular release.
Apart from the default version, legacy versions of Python or beta
releases of future upstream versions may be included as well in Debian,
as long as they are needed by other packages, or as long as it seems
reasonable to provide them.
Note: For the scope of this document, a Python version is synonymous
with all micro versions within that minor version.
e.g. Python 3.5.0 and 3.5.1 are micro versions of the same Python
version 3.5, but Python 3.4 and 3.5 are indeed different versions.
For any version, the main binary package must be called
<code class="samp docutils literal notranslate">pythonX.Y</code>.
The set of currently supported Python 3 versions can be found in
<code class="file docutils literal notranslate">/usr/share/python3/debian_defaults</code>; the supported interface to
this information is through <code class="file docutils literal notranslate">/usr/bin/py3versions</code>.
The set of currently supported Python 2 versions can be found in
<code class="file docutils literal notranslate">/usr/share/python/debian_defaults</code>; the supported interface to
this information is <code class="file docutils literal notranslate">/usr/bin/pyversions</code>.
These files are in Python <code class="docutils literal notranslate">configparser</code> format.
They define (in the <code class="docutils literal notranslate">DEFAULT</code> section) the following options:
<dl class="simple">
<dt><code class="docutils literal notranslate">default-version</code></dt><dd>The name of the interpreter for the current default Debian Python.
</dd>
<dt><code class="docutils literal notranslate">supported-versions</code></dt><dd>The set of interpreter names currently supported and for which
modules should be built and byte-compiled.
This includes <code class="docutils literal notranslate">default-version</code>.
</dd>
<dt><code class="docutils literal notranslate">old-versions</code></dt><dd>The set of interpreter names which might still be on the system but
for which modules should not be built.
</dd>
<dt><code class="docutils literal notranslate">unsupported-versions</code></dt><dd>The set of interpreter names which should not be supported at all,
that is modules should not be built or byte-compiled for these.
This includes (is a superset of) <code class="docutils literal notranslate">old-versions</code>.
</dd>
</dl>
Newer versions might also appear in <code class="docutils literal notranslate">unsupported-versions</code> before
being moved to <code class="docutils literal notranslate">supported-versions</code>.
</section>
<section id="main-packages">
<h3>3.2. Main packages<a class="headerlink" href="#main-packages" title="Permalink to this headline">¶</a></h3>
For every Python version provided in Debian, the binary package
<code class="samp docutils literal notranslate">pythonX.Y</code> shall provide a complete distribution for
deployment of Python scripts and applications.
The package must ensure that the binary <code class="file docutils literal notranslate">/usr/bin/pythonX.Y</code>
is provided.
Installation of <code class="samp docutils literal notranslate">pythonX.Y</code> shall provide the modules of the
upstream Python distribution with some exceptions.
Excluded are modules that cannot be included for licensing reasons, for
dependency tracking purposes (for example the GPL-licensed <code class="docutils literal notranslate">gdbm</code>
module), or that should not be included for packaging reasons (for
example the <code class="docutils literal notranslate">tk</code> module which depends on Xorg and the <code class="docutils literal notranslate">venv</code> module
which depends on wheels to bootstrap pip).
Modules that would interfere with system package management (for example
<code class="docutils literal notranslate">ensurepip</code>, when used outside virtual environments) are modified to
print a message explaining the problem and recommending alternatives.
Excluded are modules that cannot be included for licensing reasons (for
example the <code class="docutils literal notranslate">profile</code> module), for dependency tracking purposes (for
example the GPL-licensed <code class="docutils literal notranslate">gdbm</code> module), or that should not be
included for packaging reasons (for example the <code class="docutils literal notranslate">tk</code> module which
depends on Xorg).
Some tools and files for the development of Python modules are split
off in a separate binary package <code class="samp docutils literal notranslate">pythonX.Y-dev</code>.
Modules only used for building of Python modules (e.g. <code class="docutils literal notranslate">distutils</code>
and <code class="docutils literal notranslate">lib2to3</code>) are split into separate packages.
The <code class="docutils literal notranslate">python3-venv</code> binary package depends on these.
Documentation will be provided separately as well.
At any time, the <code class="docutils literal notranslate">python3</code> binary package must ensure that
<code class="file docutils literal notranslate">/usr/bin/python3</code> is provided, as a symlink to the current
<code class="samp docutils literal notranslate">python3.Y</code> executable.
The package must depend on the <code class="samp docutils literal notranslate">python3.Y</code> package that installs
the executable.
A <code class="docutils literal notranslate">python3-full</code> binary package must ensure that the entire Python
standard library is available, including all modules split into separate
packages (but excluding modules excluded from Debian for licensing
reasons).
This package exists for the convenience of python developers, and must
not be used in dependencies, recommendations and build dependencies by
python module or application packages.
The version of the <code class="docutils literal notranslate">python3</code> package must be greater than or equal to
<code class="samp docutils literal notranslate">3.Y</code> and lower than <code class="samp docutils literal notranslate">3.Y+1</code>.
The <code class="docutils literal notranslate">python</code> and <code class="docutils literal notranslate">python-dbg</code> binary packages are to be removed for
Bullseye.
If any Python 2 packages remain in Bullseye, these must depend on
<code class="docutils literal notranslate">python2</code> or <code class="docutils literal notranslate">python2-dbg</code>.
The <code class="docutils literal notranslate">python2</code> package must depend on the <code class="samp docutils literal notranslate">python2.Y</code> package
that installs the executable <code class="file docutils literal notranslate">/usr/bin/python2</code>.
The version of the <code class="docutils literal notranslate">python2</code> package must be greater than or equal to
<code class="samp docutils literal notranslate">2.Y</code> and lower than <code class="samp docutils literal notranslate">2.Y+1</code>.
The <code class="docutils literal notranslate">python2</code> must not provide <code class="file docutils literal notranslate">/usr/bin/python</code>.
For as long as it remains supported, the <code class="docutils literal notranslate">python</code> binary package must
ensure that <code class="file docutils literal notranslate">/usr/bin/python2</code> is provided, as a symlink to the
current <code class="samp docutils literal notranslate">python2.Y</code> executable.
The package must depend on the <code class="samp docutils literal notranslate">python2.Y</code> package that installs
the executable.
The <code class="docutils literal notranslate">python</code> binary package must also ensure that
<code class="file docutils literal notranslate">/usr/bin/python</code> is provided, as a symlink to the current
<code class="samp docutils literal notranslate">python2.Y</code> executable.
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0394">PEP 394</a> for details.
The version of the <code class="docutils literal notranslate">python</code> package must be greater than or equal to
<code class="samp docutils literal notranslate">2.Y</code> and lower than <code class="samp docutils literal notranslate">2.Y+1</code>.
</section>
<section id="minimal-packages">
<h3>3.3. Minimal packages<a class="headerlink" href="#minimal-packages" title="Permalink to this headline">¶</a></h3>
For every Python version provided in Debian, the binary package
<code class="samp docutils literal notranslate">pythonX.Y-minimal</code> might exist and should not be depended
upon by other packages except the Python runtime packages themselves.
</section>
<section id="python-interpreter">
<h3>3.4. Python Interpreter<a class="headerlink" href="#python-interpreter" title="Permalink to this headline">¶</a></h3>
<section id="interpreter-name">
<h4>3.4.1. Interpreter Name<a class="headerlink" href="#interpreter-name" title="Permalink to this headline">¶</a></h4>
The different Python major versions require different interpreters
(see <a class="reference internal" href="#main-packages">Main packages</a>).
Python scripts that require the default Python 3 version should specify
<code class="docutils literal notranslate">python3</code> as the interpreter name.
Python scripts that require the default Python 2 version should specify
<code class="docutils literal notranslate">python2</code> as the interpreter name for as long as this remains supported.
Python scripts should not specify <code class="docutils literal notranslate">python</code> as the interpreter name
even if they do not require any particular version of Python as the
script would stop working upon removal of the Python 2 stack.
Python scripts that only work with a specific Python minor version must
explicitly use the versioned interpreter name (<code class="samp docutils literal notranslate">pythonX.Y</code>).
</section>
<section id="interpreter-location">
<h4>3.4.2. Interpreter Location<a class="headerlink" href="#interpreter-location" title="Permalink to this headline">¶</a></h4>
Python scripts should specify the Debian Python interpreter, to ensure
that the Debian Python installation is used and all dependencies on
additional Python modules are met.
The preferred specification for the Python 3 interpreter is
<code class="file docutils literal notranslate">/usr/bin/python3</code> (or <code class="file docutils literal notranslate">/usr/bin/python3.Y</code> if it requires
Python <code class="samp docutils literal notranslate">3.Y</code>).
The preferred specification for the Python 2 interpreter is
<code class="file docutils literal notranslate">/usr/bin/python2</code> (or <code class="file docutils literal notranslate">/usr/bin/python2.Y</code> if it requires
Python <code class="samp docutils literal notranslate">2.Y</code>).
Scripts requiring the default Python 2 version must not specify the
interpreter <code class="file docutils literal notranslate">/usr/bin/python</code> as such scripts will fail when the
unversioned interpreter binary <code class="file docutils literal notranslate">/usr/bin/python</code> is removed.
Maintainers should not override the Debian Python interpreter using
<code class="samp docutils literal notranslate">/usr/bin/env name</code>.
This is not advisable as it bypasses Debian’s dependency checking and
makes the package vulnerable to incomplete local installations of
Python.
</section>
</section>
<section id="module-path">
<h3>3.5. Module Path<a class="headerlink" href="#module-path" title="Permalink to this headline">¶</a></h3>
By default, Python modules are searched in the directories listed in the
<code class="xref std std-envvar docutils literal notranslate">PYTHONPATH</code> environment variable and in the <code class="docutils literal notranslate">sys.path</code> Python
variable.
For all supported Debian releases, <code class="docutils literal notranslate">sys.path</code> does not include a
<code class="file docutils literal notranslate">/usr/lib/pythonXY.zip</code> entry.
Directories with private Python modules must be absent from the <code class="docutils literal notranslate">sys.path</code>.
Public Python 3 modules must be installed in the system Python 3 modules
directory, <code class="file docutils literal notranslate">/usr/lib/python3/dist-packages</code>.
Public Python 2 modules must be installed in the system Python 2 modules
directory <code class="file docutils literal notranslate">/usr/lib/python2.Y/dist-packages</code>, where
<code class="samp docutils literal notranslate">2.Y</code> is the Python 2 version.
A special directory is dedicated to public Python modules installed by
the local administrator, <code class="file docutils literal notranslate">/usr/local/lib/python3/dist-packages</code>
for all Python 3 versions,
<code class="file docutils literal notranslate">/usr/local/lib/python2.Y/dist-packages</code> for Python 2.
For local installation of Python modules by the system administrator,
special directories are reserved.
The directory <code class="file docutils literal notranslate">/usr/local/lib/python3/site-packages</code> is in the
Python 3 runtime module search path.
The directory <code class="file docutils literal notranslate">/usr/local/lib/python2.Y/site-packages</code> is in the
Python <code class="samp docutils literal notranslate">2.Y</code> runtime module search path.
Additional information on appending site-specific paths to the module
search path is available in the official documentation of the <code class="docutils literal notranslate">site</code>
module.
Python modules which work with multiple supported Python 2 versions must
install to version-specific locations, for instance
<code class="file docutils literal notranslate">/usr/lib/python2.6/dist-packages/foo.py</code> and
<code class="file docutils literal notranslate">/usr/lib/python2.7/dist-packages/foo.py</code>.
These should point to a common file.
Architecture-independent public Python 3 modules must be installed to
<code class="file docutils literal notranslate">/usr/lib/python3/dist-packages</code>.
Architecture-independent public Python 2 modules should be installed to
<code class="file docutils literal notranslate">/usr/lib/python2.7/dist-packages</code>.
The historical location for this was <code class="file docutils literal notranslate">/usr/share/pyshared</code>.
Since Python 2.7 is the last Python 2 version and the only supported
version in Wheezy and later releases, a version-specific location is
sufficient.
</section>
<section id="hooks-for-updates-to-installed-runtimes">
<h3>3.6. Hooks for updates to installed runtimes<a class="headerlink" href="#hooks-for-updates-to-installed-runtimes" title="Permalink to this headline">¶</a></h3>
The <code class="docutils literal notranslate">python3</code> binary package has special hooks to allow other packages
to act upon updates to the installed runtimes.
This mechanism is required to handle changes of the default Python
runtime in some packages and to enable the Python packaging helpers.
There are three supported hook types which come in the form of scripts
which are invoked from the maintainer scripts of the Python runtime
packages when specific installations, removals, or upgrades occur.
<ol class="arabic simple">
<li><code class="file docutils literal notranslate">/usr/share/python3/runtime.d/*.rtinstall</code>:
These are called when a runtime is installed or becomes supported.
The first argument is <code class="docutils literal notranslate">rtinstall</code>, the second argument is the
affected runtime (for example <code class="samp docutils literal notranslate">pythonX.Y</code>) and the third
and fourth argument are the old and new version of this packaged
runtime if this runtime was already installed but unsupported.</li>
<li><code class="file docutils literal notranslate">/usr/share/python3/runtime.d/*.rtremove</code>:
These are called when a runtime is removed or stops being supported.
The first argument is <code class="docutils literal notranslate">rtremove</code>, and the second argument is the
affected runtime (for example <code class="samp docutils literal notranslate">pythonX.Y</code>).</li>
<li><code class="file docutils literal notranslate">/usr/share/python3/runtime.d/*.rtupdate</code>:
These are called when the default runtime changes.
The first argument is either <code class="docutils literal notranslate">pre-rtupdate</code>, called before changing
the default runtime, or <code class="docutils literal notranslate">rtupdate</code>, called when changing the
default runtime, or <code class="docutils literal notranslate">post-rtupdate</code>, called immediately afterwards.
The second argument is the old default runtime (for example
<code class="samp docutils literal notranslate">pythonX.Y</code>), and the third argument is the new default
runtime (for example <code class="samp docutils literal notranslate">pythonX.Z</code>).</li>
</ol>
</section>
<section id="documentation">
<h3>3.7. Documentation<a class="headerlink" href="#documentation" title="Permalink to this headline">¶</a></h3>
Python documentation is split out in separate binary packages
<code class="samp docutils literal notranslate">pythonX.Y-doc</code>.
The binary package <code class="docutils literal notranslate">python3-doc</code> will always provide the documentation
for the default Debian Python 3 version.
The binary package <code class="docutils literal notranslate">python2-doc</code> will always provide the documentation
for the default Debian Python 2 version, for as long as that remains
supported.
TODO: Policy for documentation of third party packages.
</section>
</section>
<section id="packaged-modules">
<h2>4. Packaged Modules<a class="headerlink" href="#packaged-modules" title="Permalink to this headline">¶</a></h2>
The goal of these policies is to reduce the work necessary for Python
transitions.
Python modules are internally very dependent on a specific Python
version.
However, we want to automate recompiling modules when possible, either
during the upgrade itself (re-compiling bytecode files <code class="file docutils literal notranslate">*.pyc</code>
and <code class="file docutils literal notranslate">*.pyo</code>) or shortly thereafter with automated rebuilds (to
handle C extensions).
These policies encourage automated dependency generation and loose
version bounds whenever possible.
<section id="types-of-python-modules">
<h3>4.1. Types of Python Modules<a class="headerlink" href="#types-of-python-modules" title="Permalink to this headline">¶</a></h3>
There are two kinds of Python modules, “pure” Python modules, and
extension modules.
Pure Python modules are Python source code that generally works across
many versions of Python.
Extensions are C code compiled and linked against a specific version of
the Python runtime, and so can only be used by one version of Python.
Debian Python does not link extensions to <code class="docutils literal notranslate">libpython</code> (as is done in
some operating systems).
Symbols are resolved by <code class="file docutils literal notranslate">/usr/bin/pythonX.Y</code> which is not
linked to <code class="docutils literal notranslate">libpython</code>.
Python packages are a way of structuring Python’s module namespace by
using “dotted module names”.
See <a class="reference external" href="https://docs.python.org/3/glossary.html#term-package">Python’s glossary</a> for details on
how packages are defined in Python terms (a package in the Python sense
is unrelated to a Debian package).
Python packages must be packaged into the same directory (as done by
upstream).
Splitting components of a package across directories changes the import
order and may confuse documentation tools and IDEs.
There are two ways to distribute Python modules.
Public modules are installed in a public directory as listed in
<a class="reference internal" href="index.html#module-path">Module Path</a>.
They are accessible to any program.
Private modules are installed in a private directory such as
<code class="file docutils literal notranslate">/usr/share/package-name</code> or <code class="file docutils literal notranslate">/usr/lib/package-name</code>.
They are generally only accessible to a specific program or suite of
programs included in the same package.
</section>
<section id="wheels">
<h3>4.2. Wheels<a class="headerlink" href="#wheels" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0427">PEP 427</a> defines a built-package format called “wheels”, which is a
Zip format archive containing Python code and a <code class="file docutils literal notranslate">*.dist-info</code>
metadata directory, in a single file named with the <code class="docutils literal notranslate">.whl</code> suffix.
As Zip files, wheels containing pure Python can be put on <code class="docutils literal notranslate">sys.path</code>
and modules in the wheel can be imported directly by Python’s <code class="docutils literal notranslate">import</code>
statement.
(Importing extension modules from wheels is not yet supported as of
Python 3.4.)
Except as described below, packages must not build or provide wheels.
They are redundant to the established way of providing Python libraries
to Debian users, take no advantage of distro-based tools, and are less
convenient to use.
E.g. they must be explicitly added to <code class="docutils literal notranslate">sys.path</code>, cannot be easily
grepped, and stack traces through Zip files are more difficult to debug.
A very limited set of wheel packages are available in the archive, but
these support the narrow purpose of enabling the <code class="docutils literal notranslate">pip</code>,
<code class="docutils literal notranslate">virtualenv</code>, and <code class="docutils literal notranslate">pyvenv</code> tools in a Debian policy compliant way.
These packages build their own dependent wheels through the use of the
<code class="docutils literal notranslate">dirtbike</code> “rewheeling” tool, which takes installed Debian packages
and turns them back into wheels.
Only universal wheels (i.e. pure-Python, Python 3 and 2 compatible
packages) are supported, with the exception of wheels of packages that
no longer support Python 2.
Wheels built for these packages are not required to be universal.
Since only the programs that require wheels need build them, only they
may provide <code class="docutils literal notranslate">-whl</code> packages, e.g. <code class="docutils literal notranslate">python3-pip-whl</code>.
When these binary packages are installed, <code class="file docutils literal notranslate">*.whl</code> files must be
placed in the <code class="file docutils literal notranslate">/usr/share/python-wheels</code> directory.
The location inside a virtual environment will be rooted in the virtual
environment, instead of <code class="file docutils literal notranslate">/usr</code>.
</section>
<section id="module-package-names">
<h3>4.3. Module Package Names<a class="headerlink" href="#module-package-names" title="Permalink to this headline">¶</a></h3>
Public Python modules must be packaged separately by major Python
version, to preserve run time separation between Python 2 and Python 3.
Public Python 3 modules used by other packages must have their binary
package name prefixed with <code class="docutils literal notranslate">python3-</code>.
It is recommended to use this prefix for all packages with public
modules as they may be used by other packages in the future.
The binary package for module <code class="samp docutils literal notranslate">foo</code> should preferably be named
<code class="samp docutils literal notranslate">python3-foo</code>, if the module name allows.
This is not required if the binary package installs multiple modules, in
which case the maintainer shall choose the name of the module which best
represents the package.
For the purposes of package naming, the name that is used for a module
is the name that can be used with <code class="docutils literal notranslate">import</code>, which is not necessarily
the same as the name used in setuptools <code class="docutils literal notranslate">PKG-INFO</code> and <code class="docutils literal notranslate">.egg-info</code>
files and directories.
For example, the module described in <code class="samp docutils literal notranslate">pyxdg-*.egg-info</code> is used
via <code class="docutils literal notranslate">import xdg</code>, so its package name is <code class="docutils literal notranslate">python3-xdg</code> and not
<code class="docutils literal notranslate">python3-pyxdg</code>.
Some modules have names that contain underscores or capital letters,
which are not allowed in Debian package names.
The recommendation is to replace underscores with hyphen/minus and
capital letters with lower-case.
For example, the modules that can be used with <code class="docutils literal notranslate">import distro_info</code>
and <code class="docutils literal notranslate">import Xlib</code> are packaged as <code class="docutils literal notranslate">python3-distro-info</code> and
<code class="docutils literal notranslate">python3-xlib</code> respectively.
For subpackages such as <code class="samp docutils literal notranslate">foo.bar</code>, the recommendation is to name
the binary package <code class="samp docutils literal notranslate">python3-foo.bar</code>.
Such a package should support the current Debian Python version,
and more if possible (there are several tools to help implement
this, see <a class="reference internal" href="index.html#packaging-tools">Packaging Tools</a>).
For example, if Python 3.3, 3.4, and 3.5 are supported, the Python
statement
<div class="highlight-python notranslate"><div class="highlight"><pre>import foo
</pre></div>
</div>
should import the module when the program interpreter is any of
<code class="file docutils literal notranslate">/usr/bin/python3.3</code>, <code class="file docutils literal notranslate">/usr/bin/python3.4</code>, and
<code class="file docutils literal notranslate">/usr/bin/python3.5</code>.
This requirement also applies to extension modules; binaries for all the
supported Python versions should be included in a single package.
Packages intended for use with Django (<code class="docutils literal notranslate">python3-django</code>) are installed
in the same namespace as other python packages for a variety of reasons.
Many such packages are named <code class="samp docutils literal notranslate">django_name</code> upstream.
These are then packaged as <code class="samp docutils literal notranslate">python3-django-name</code>.
This makes it clear that they are intended for use with Django and not
general purpose Python modules.
Debian maintainers are encouraged to work with their upstreams to
support consistent use of this approach.
If the documentation for a module <code class="samp docutils literal notranslate">foo</code> provided in
<code class="samp docutils literal notranslate">python3-foo</code> is large enough that a separate binary package for
documentation is desired, then the documentation package should
preferably be named <code class="samp docutils literal notranslate">python-foo-doc</code> (and in particular, not
<code class="samp docutils literal notranslate">python3-foo-doc</code>).
</section>
<section id="specifying-supported-versions">
<h3>4.4. Specifying Supported Versions<a class="headerlink" href="#specifying-supported-versions" title="Permalink to this headline">¶</a></h3>
The <code class="file docutils literal notranslate">debian/control</code> source paragraph may contain optional fields
to specify the versions of Python the package supports.
The optional <code class="docutils literal notranslate">X-Python3-Version</code> field specifies the versions of
Python 3 supported.
When not specified, it defaults to all currently supported Python 3
versions.
Similarly, the optional fields <code class="docutils literal notranslate">X-Python-Version</code> or
<code class="docutils literal notranslate">XS-Python-Version</code> were used to specify the versions of Python 2
supported by the source package.
They are obsolete and must be removed.
These fields are used by some packaging scripts to automatically
generate appropriate Depends and Provides lines.
The format of the field may be one of the following:
<div class="highlight-default notranslate"><div class="highlight"><pre>X-Python3-Version: &gt;= X.Y
X-Python3-Version: &gt;= A.B, &lt;&lt; X.Y
XS-Python-Version: A.B, X.Y
</pre></div>
</div>
The keyword <code class="docutils literal notranslate">all</code> is no longer to be used since using version numbers
is clearer than <code class="docutils literal notranslate">all</code> and encodes more information.
The keyword <code class="docutils literal notranslate">all</code> must be ignored for Python 3 versions.
A comma-separated list of multiple individual versions (e.g. <code class="docutils literal notranslate">3.3, 3.4,
3.5</code>) in <code class="docutils literal notranslate">XS-Python-Version</code> will continue to be supported, but
is not recommended.
The use of multiple individual versions in <code class="docutils literal notranslate">X-Python-Version</code> or
<code class="docutils literal notranslate">X-Python3-Version</code> is not supported for Wheezy and later releases.
The keyword <code class="docutils literal notranslate">current</code> has been deprecated and must not be used.
It must be ignored for Python 3 versions.
The use of <code class="docutils literal notranslate">XB-Python-Version</code> in the binary package paragraphs of
<code class="file docutils literal notranslate">debian/control</code> file has been deprecated and should be removed in
the normal course of package updates.
It never achieved sufficient deployment to support its intended purpose
of managing Python transitions.
This purpose can be adequately accomplished by examining package
dependencies.
</section>
<section id="dependencies">
<h3>4.5. Dependencies<a class="headerlink" href="#dependencies" title="Permalink to this headline">¶</a></h3>
Any package that installs modules for the default Python version (or
many versions including the default) as described in
<a class="reference internal" href="#module-package-names">Module Package Names</a>, must declare a dependency on the default
Python runtime package.
If it requires other modules to work, the package must declare
dependencies on the corresponding packaged modules.
The package must not declare dependency on any version-specific Python
runtime or module package.
For Python 3, the correct dependencies are <code class="samp docutils literal notranslate">Depends:
python3 (&gt;= 3.Y)</code> and any corresponding <code class="samp docutils literal notranslate">python3-foo</code>
packages.
If any Python 2 packages remain, the correct dependencies are
<code class="samp docutils literal notranslate">Depends: python2 (&gt;= 2.Y)</code> and any corresponding
<code class="samp docutils literal notranslate">python2-foo</code> packages.
Any package that installs Python modules or Python 3 binary extensions
must also declare a maximum version it supports as currently built.
This is accomplished by declaring a maximum version constraint strictly
less than one higher than the current maximum version, i.e.
<code class="samp docutils literal notranslate">Depends: python3 (&lt;&lt; X.Y)</code>.
</section>
<section id="provides">
<h3>4.6. Provides<a class="headerlink" href="#provides" title="Permalink to this headline">¶</a></h3>
Binary packages that declare Provides dependencies of the form
<code class="samp docutils literal notranslate">pythonX.Y-foo</code> were never supported for Python 3.
They should be removed in the normal course of package updates.
Future provision of values for the substitution variable
<code class="docutils literal notranslate">python:Provides</code> is not guaranteed.
</section>
<section id="modules-byte-compilation">
<h3>4.7. Modules Byte-Compilation<a class="headerlink" href="#modules-byte-compilation" title="Permalink to this headline">¶</a></h3>
If a binary package provides any binary-independent modules
(<code class="file docutils literal notranslate">foo.py</code> files), the corresponding byte-compiled modules
(<code class="file docutils literal notranslate">foo.pyc</code> files) and optimized modules (<code class="file docutils literal notranslate">foo.pyo</code>
files) must not ship in the package.
Instead, they should be generated in the package’s post-install script,
and removed in the package’s pre-remove script.
The package’s <code class="file docutils literal notranslate">prerm</code> has to make sure that both <code class="file docutils literal notranslate">foo.pyc</code>
and <code class="file docutils literal notranslate">foo.pyo</code> are removed.
A binary package should only byte-compile the files which belong to the
package.
The file <code class="file docutils literal notranslate">/etc/python/debian_config</code> allows configuration how
modules should be byte-compiled.
The post-install scripts should respect these settings.
Pure Python modules in private installation directories that are
byte-compiled with the default Python version must be forcefully
byte-compiled again when the default Python version changes.
Public Python extensions should be bin-NMUed.
Private Python extensions should be subject to binary NMUs every time
the default interpreter changes, unless the extension is updated through
a <code class="file docutils literal notranslate">*.rtupdate</code> script.
</section>
</section>
<section id="python-programs">
<h2>5. Python Programs<a class="headerlink" href="#python-programs" title="Permalink to this headline">¶</a></h2>
<section id="interpreter-directive-shebang">
<h3>5.1. Interpreter directive (“Shebang”)<a class="headerlink" href="#interpreter-directive-shebang" title="Permalink to this headline">¶</a></h3>
Executables written for interpretation by Python must use an appropriate
interpreter directive, or “shebang”, as the first line of the program.
This line should be of the form <code class="samp docutils literal notranslate">#!interpreter_location</code>.
See <a class="reference internal" href="index.html#interpreter-name">Interpreter Name</a> for the interpreter name to use.
As noted in <a class="reference internal" href="index.html#interpreter-location">Interpreter Location</a>, the form <code class="samp docutils literal notranslate">#!/usr/bin/env
interpreter_name</code> is deprecated.
</section>
<section id="programs-using-the-default-python">
<h3>5.2. Programs using the default Python<a class="headerlink" href="#programs-using-the-default-python" title="Permalink to this headline">¶</a></h3>
A package that installs a program that can be run by any version of
Python 3 must declare a dependency on <code class="docutils literal notranslate">python3</code>, with a versioned
dependency if necessary.
A package that installs a program that can be run by any version of
Python 2 must declare a dependency on <code class="docutils literal notranslate">python2</code>, with a versioned
dependency if necessary.
If the program needs the public Python module <code class="docutils literal notranslate">foo</code>, the package must
depend on the binary package that installs the <code class="docutils literal notranslate">foo</code> module.
See <a class="reference internal" href="index.html#module-package-names">Module Package Names</a> for the naming of packages that install
public Python modules.
</section>
<section id="programs-shipping-private-modules">
<h3>5.3. Programs Shipping Private Modules<a class="headerlink" href="#programs-shipping-private-modules" title="Permalink to this headline">¶</a></h3>
A program that specifies <code class="docutils literal notranslate">python3</code> as its interpreter may require its
own private Python modules.
These modules should be installed in <code class="file docutils literal notranslate">/usr/share/module</code>, or
<code class="file docutils literal notranslate">/usr/lib/module</code> if the modules are architecture-dependent
(e.g. extensions).
The rules explained in <a class="reference internal" href="index.html#module-byte-compilation">Modules Byte-Compilation</a> apply to those
private modules: the byte-compiled modules must not be shipped with the
binary package, they should be generated in the package’s post-install
script using the current default Python version, and removed in the
pre-remove script.
Modules should be byte-compiled using the current default Python
version.
Programs that have private compiled extensions must either handle
multiple version support themselves, or declare a tight dependency on
the current Python version (e.g. <code class="docutils literal notranslate">Depends: python3 (&gt;= 3.5),
python3 (&lt;&lt; 3.6)</code>.
</section>
<section id="programs-using-a-particular-python-version">
<h3>5.4. Programs Using a Particular Python Version<a class="headerlink" href="#programs-using-a-particular-python-version" title="Permalink to this headline">¶</a></h3>
A program which requires a specific minor version of Python must specify
the versioned interpreter <code class="samp docutils literal notranslate">pythonX.Y</code>.
The package that installs the programs must also specify a dependency on
<code class="samp docutils literal notranslate">pythonX.Y</code> and on any packages that install necessary
modules.
The notes on installation directories and byte-compilation for programs
that support any version of Python also apply to programs supporting
only a single Python version.
Modules to be byte-compiled should use the same Python version as the
package itself.
</section>
</section>
<section id="programs-embedding-python">
<h2>6. Programs Embedding Python<a class="headerlink" href="#programs-embedding-python" title="Permalink to this headline">¶</a></h2>
<section id="building-embedded-programs">
<h3>6.1. Building Embedded Programs<a class="headerlink" href="#building-embedded-programs" title="Permalink to this headline">¶</a></h3>
Any package that installs a program which embeds a Python interpreter
must declare <code class="docutils literal notranslate">Build-Depends</code> on <code class="samp docutils literal notranslate">pythonX.Y-dev</code>, where
<code class="samp docutils literal notranslate">X.Y</code> is the Python version the program builds against.
It should be the current default Python version unless the program does
not work correctly with this version.
</section>
<section id="embedded-python-dependencies">
<h3>6.2. Embedded Python Dependencies<a class="headerlink" href="#embedded-python-dependencies" title="Permalink to this headline">¶</a></h3>
Dependencies for programs linking against the shared Python library will
be automatically created by <code class="docutils literal notranslate">dpkg-shlibdeps</code>.
The <code class="samp docutils literal notranslate">libpythonX.Y.so.Z</code> library the program is built against
is provided by the <code class="samp docutils literal notranslate">pythonX.Y</code> package.
</section>
</section>
<section id="interaction-with-locally-installed-python-versions">
<h2>7. Interaction with Locally Installed Python Versions<a class="headerlink" href="#interaction-with-locally-installed-python-versions" title="Permalink to this headline">¶</a></h2>
As long as you don’t install other versions of Python in your path,
Debian’s Python versions won’t be affected by a new version.
If you install a different micro version of the version of Python you
have got installed, you will need to be careful to install all the
modules you use for that version of Python too.
</section>
</div>
<div class="toctree-wrapper compound" id="appendix">
<section id="build-dependencies">
<h2>1. Build Dependencies<a class="headerlink" href="#build-dependencies" title="Permalink to this headline">¶</a></h2>
Build dependencies for Python-dependent packages must be declared for
every Python version that the package is built for.
The <code class="docutils literal notranslate">python3-all-dev</code> should be used when building extensions for any
or all Python 3 versions.
The <code class="docutils literal notranslate">python-all-dev</code> should be used when building extensions for any
or all Python 2 versions.
To build for a specific version or versions, declare <code class="docutils literal notranslate">Build-Depends</code>
on <code class="samp docutils literal notranslate">pythonX.Y-dev</code>.
Some applications and pure Python modules may be able to avoid
dependency on the <code class="docutils literal notranslate">-dev</code> packages, and declare <code class="docutils literal notranslate">Build-Depends</code> on
the runtime environment only
(<code class="docutils literal notranslate">python3</code>, <code class="docutils literal notranslate">python3-all</code>, <code class="docutils literal notranslate">python2</code>, <code class="docutils literal notranslate">python2-all</code>).
A package that does not require the <code class="docutils literal notranslate">-dev</code> packages must not declare
<code class="docutils literal notranslate">Build-Depends</code> on them.
Declare <code class="docutils literal notranslate">Build-Depends</code> on at least:
<div class="highlight-default notranslate"><div class="highlight"><pre>Build-Depends: python2.7
Build-Depends: python2.6 (&gt;= 2.6-1)
Build-Depends: python (&gt;= 2.6.6-9)
Build-Depends: python-all

Build-Depends: python2.7-dev
Build-Depends: python3.5-dev (&gt;= 3.5.1-1)
Build-Depends: python-dev (&gt;= 2.6.6-9)
Build-Depends: python-all-dev
Build-Depends: python3-all-dev (&gt;= 3.2)
</pre></div>
</div>
</section>
<section id="packaging-tools">
<h2>2. Packaging Tools<a class="headerlink" href="#packaging-tools" title="Permalink to this headline">¶</a></h2>
This section describes the various tools to help package Python programs
and modules for Debian.
Although none of these tools are mandatory, their use is strongly
encouraged, as the above policy has been designed with them in mind (and
vice versa).
This appendix is just an overview.
If you use these tools, you should read their full documentation.
<section id="distutils">
<h3>2.1. distutils<a class="headerlink" href="#distutils" title="Permalink to this headline">¶</a></h3>
The standard Python <code class="docutils literal notranslate">distutils</code> module has been modified in Debian to
change the default installation directory of public Python modules and
to add a new flag to the <code class="docutils literal notranslate">install</code> command to override the default,
<code class="docutils literal notranslate">--install-layout=</code>.
Public Python modules installed with a modified distutils default to
<code class="file docutils literal notranslate">/usr/local/lib/pythonX.Y/dist-packages</code> for Python 2.6 and
later.
This directory is seen by the system-provided Python 2.6.
When using a local Python installation, the default is
<code class="file docutils literal notranslate">/usr/local/lib/pythonX.Y/site-packages</code> which is only seen by
the local Python installation.
Using the <code class="docutils literal notranslate">--install-layout=deb</code> flag to the <code class="docutils literal notranslate">install</code> command of
<code class="file docutils literal notranslate">setup.py</code> with a system-provided Python 2.6 or later versions,
Python modules will be installed to
<code class="file docutils literal notranslate">/usr/lib/pythonX.Y/dist-packages</code> which is only seen by the
system-provided Python, not by a local installation.
</section>
<section id="setuptools">
<h3>2.2. setuptools<a class="headerlink" href="#setuptools" title="Permalink to this headline">¶</a></h3>
The related Python <code class="docutils literal notranslate">setuptools</code> module has been modified in Debian
along the same lines as <code class="docutils literal notranslate">distutils</code>.
Upstream focus on developments and improvements for Python packaging
tools has largely shifted away from <code class="docutils literal notranslate">distutils</code> and to <code class="docutils literal notranslate">setuptools</code>.
They offer a similar API and at some point in the future, <code class="docutils literal notranslate">setuptools</code>
may fully replace <code class="docutils literal notranslate">distutils</code> in Debian package builds.
</section>
<section id="dh-python">
<h3>2.3. dh-python<a class="headerlink" href="#dh-python" title="Permalink to this headline">¶</a></h3>
<code class="docutils literal notranslate">dh-python</code> provides extensions for <code class="docutils literal notranslate">debhelper</code> to make it easier to
package Python modules and extensions.
They calculate Python dependencies, add maintainer scripts to byte
compile files, etc.
Their use is not mandatory, but they are recommended by the Debian
Python maintainers.
See <a class="reference external" href="https://manpages.debian.org/dh_python3">man dh_python3</a> for
details.
</section>
<section id="pybuild">
<h3>2.4. pybuild<a class="headerlink" href="#pybuild" title="Permalink to this headline">¶</a></h3>
Pybuild is a Debian Python specific build system that invokes various
build systems for requested Python versions in order to build modules
and extensions.
It supports automatically building for multiple Python versions.
</section>
<section id="cdbs">
<h3>2.5. CDBS<a class="headerlink" href="#cdbs" title="Permalink to this headline">¶</a></h3>
The CDBS <code class="file docutils literal notranslate">python-distutils.mk</code> class helps packaging of distutils
based Python packages.
</section>
<section id="python-support-removed">
<h3>2.6. python-support (removed)<a class="headerlink" href="#python-support-removed" title="Permalink to this headline">¶</a></h3>
<code class="docutils literal notranslate">python-support</code> provided another way to manage Python modules.
It has been removed from Debian Stretch and later releases.
</section>
<section id="python-central-removed">
<h3>2.7. python-central (removed)<a class="headerlink" href="#python-central-removed" title="Permalink to this headline">¶</a></h3>
<code class="docutils literal notranslate">python-central</code> provided another way to manage Python modules.
It has been removed from Debian Jessie and later releases.
</section>
</section>
<section id="upgrade-procedure">
<h2>3. Upgrade Procedure<a class="headerlink" href="#upgrade-procedure" title="Permalink to this headline">¶</a></h2>
This section describes the procedure for the upgrade when the
default Python version is changed in the Debian <code class="docutils literal notranslate">unstable</code> release,
requiring recompilation of many Python-related packages.
<ol class="arabic simple">
<li>Selected pre-releases and release candidates of new Python versions
are uploaded to Debian <code class="docutils literal notranslate">experimental</code> to support pre-transition
work and testing.</li>
<li>Application and module maintainers make sourceful changes where
needed to prepare for the new Python version when needed.</li>
<li>Have a long and heated discussion.</li>
<li>The Debian Python maintainer and module/application maintainers
discuss the readiness for a new default Debian Python version and
associated packaging/policy changes.
Once there is some consensus, the Python maintainer announces the
upgrade and uploads to <code class="docutils literal notranslate">unstable</code>.</li>
<li>Upload of the Python core meta-packages <code class="docutils literal notranslate">python3</code>,
<code class="docutils literal notranslate">python3-dev</code>, <code class="docutils literal notranslate">python3-doc</code> and several
<code class="samp docutils literal notranslate">python3-module</code>, depending on the new <code class="samp docutils literal notranslate">python3.Y</code>,
<code class="samp docutils literal notranslate">python3.Y-dev</code> and so on.</li>
<li>The Debian release team schedules rebuilds for packages that may
need it.
Packages that require additional manual work get updated and
uploaded.</li>
</ol>
The necessary package builds are typically done in three phases in order
to keep transitions as smooth as possible.
For Python 3, there is no general need to update architecture all
packages for a new Python 3 version. Only architecture any packages need
to be rebuilt.
<ol class="arabic simple">
<li>The new Python 3 version is added to supported versions and packages
that support multiple Python 3 versions are binNMUed.
They now support both the new and older Python 3 versions.
This requires transition assistance from the release team in the form
of a transition tracker and binNMU scheduling, but is not a
transition that can cause entanglements with other transitions in
Debian.</li>
<li>Once the default Python 3 version is changed, binNMUs are done for
packages that only support one Python 3 version.
Some transient uninstallability is unavoidable.
This is a transition that can entangle other transitions in Debian
and requires more careful coordination with the release team.</li>
<li>After the old Python 3 version is dropped from supported versions
then packages with multi-version support are binNMUed again to remove
support for the old Python 3 version.
This is not a true transition and only needs a tracker and binNMU
scheduling.</li>
</ol>
</section>
<section id="this-document">
<h2>4. This document<a class="headerlink" href="#this-document" title="Permalink to this headline">¶</a></h2>
Source of this document is <code class="file docutils literal notranslate">policy/</code> in git repository
<a class="reference external" href="https://salsa.debian.org/cpython-team/python3-defaults">python3-defaults</a>.
Propose changes to this policy on the <a class="reference external" href="https://lists.debian.org/debian-python/">debian-python mailing list</a> for review.
</section>
</div>
</section>
<section id="indices-and-tables">
<h1>Indices and tables<a class="headerlink" href="#indices-and-tables" title="Permalink to this headline">¶</a></h1>
<ul class="simple">
<li><a class="reference internal" href="genindex.html">Index</a></li>
<li><a class="reference internal" href="py-modindex.html">Module Index</a></li>
<li><a class="reference internal" href="search.html">Search Page</a></li>
</ul>
</section>

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 <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="#">Table of Contents</a></h3>
 <ul>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-copyright">1. Copyright</a></li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-python3">2. Completing the move to Python 3</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#removal-of-the-unversioned-packages">2.1. Removal of the unversioned packages</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#unversioned-python-commands">2.2. Unversioned python commands</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-interpreter">3. Python Packaging</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#versions">3.1. Versions</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#main-packages">3.2. Main packages</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#minimal-packages">3.3. Minimal packages</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#python-interpreter">3.4. Python Interpreter</a><ul>
<li class="toctree-l3"><a class="reference internal" href="index.html#interpreter-name">3.4.1. Interpreter Name</a></li>
<li class="toctree-l3"><a class="reference internal" href="index.html#interpreter-location">3.4.2. Interpreter Location</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="index.html#module-path">3.5. Module Path</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#hooks-for-updates-to-installed-runtimes">3.6. Hooks for updates to installed runtimes</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#documentation">3.7. Documentation</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-packaged-modules">4. Packaged Modules</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#types-of-python-modules">4.1. Types of Python Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#wheels">4.2. Wheels</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#module-package-names">4.3. Module Package Names</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#specifying-supported-versions">4.4. Specifying Supported Versions</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#dependencies">4.5. Dependencies</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#provides">4.6. Provides</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#modules-byte-compilation">4.7. Modules Byte-Compilation</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-python-programs">5. Python Programs</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#interpreter-directive-shebang">5.1. Interpreter directive (“Shebang”)</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#programs-using-the-default-python">5.2. Programs using the default Python</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#programs-shipping-private-modules">5.3. Programs Shipping Private Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#programs-using-a-particular-python-version">5.4. Programs Using a Particular Python Version</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-embedded-python">6. Programs Embedding Python</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#building-embedded-programs">6.1. Building Embedded Programs</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#embedded-python-dependencies">6.2. Embedded Python Dependencies</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-locally-installed-python">7. Interaction with Locally Installed Python Versions</a></li>
</ul>
Appendix
<ul>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-build-dependencies">1. Build Dependencies</a></li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-packaging-tools">2. Packaging Tools</a><ul>
<li class="toctree-l2"><a class="reference internal" href="index.html#distutils">2.1. distutils</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#setuptools">2.2. setuptools</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#dh-python">2.3. dh-python</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#pybuild">2.4. pybuild</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#cdbs">2.5. CDBS</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#python-support-removed">2.6. python-support (removed)</a></li>
<li class="toctree-l2"><a class="reference internal" href="index.html#python-central-removed">2.7. python-central (removed)</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-upgrade-procedure">3. Upgrade Procedure</a></li>
<li class="toctree-l1"><a class="reference internal" href="index.html#document-this-document">4. This document</a></li>
</ul>

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