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Explicitly document Python compatibility (#17, #18, #27, #31)
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xolox committed Aug 4, 2020
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Expand Up @@ -7,47 +7,47 @@ py2deb: Python to Debian package converter
.. image:: https://coveralls.io/repos/paylogic/py2deb/badge.svg?branch=master
:target: https://coveralls.io/r/paylogic/py2deb?branch=master

The Python package `py2deb` converts Python source distributions to Debian
binary packages (the ones used for installation). It uses pip-accel_ to
download, unpack and compile Python packages. Because of this `py2deb` is
compatible with the command line interface of the ``pip install`` command. For
example you can specify packages to convert as command line arguments but you
can also use `requirement files`_ if you want.
The Python package py2deb_ converts Python source distributions to Debian
binary packages (the ones used for installation). It uses pip-accel_ (based on
pip_) to download, unpack and compile Python packages. Because of this py2deb_
is compatible with the command line interface of the ``pip install`` command.
For example you can specify packages to convert as command line arguments but
you can also use `requirement files`_ if you want.

During the conversion process dependencies are automatically taken into account
and converted as well so you don't actually have to use requirement files
including transitive dependencies. In fact you might prefer not explicitly
listing your transitive dependencies in requirement files because `py2deb` will
listing your transitive dependencies in requirement files because py2deb_ will
translate the version constraints of Python packages into Debian package
relationships.

The `py2deb` package is currently tested on CPython_ 2.7, 3.5, 3.6, 3.7 and
PyPy_ (2 and 3). Unfortunately Python 3.8+ is not yet supported, a significant
upcoming refactoring is required to resolve this. For usage instructions please
refer to the documentation hosted on `Read The Docs`_.
The py2deb_ package is currently tested on CPython_ 2.7, 3.5, 3.6, 3.7 and
PyPy_ 2 and 3. Unfortunately Python 3.8+ is not yet supported (see below). For
usage instructions please refer to the documentation hosted on `Read The
Docs`_.

.. contents::
:local:

Installation
------------

The `py2deb` package is available on PyPI_, so installation is very simple:
The py2deb_ package is available on PyPI_, so installation is very simple:

.. code-block:: console
$ pip install py2deb
There are some system dependencies which you have to install as well:

.. code-block:: sh
.. code-block:: console
$ sudo apt-get install dpkg-dev fakeroot
Optionally you can also install Lintian_ (which is not a hard dependency but
more of a "nice to have"):

.. code-block:: sh
.. code-block:: console
$ sudo apt-get install lintian
Expand All @@ -61,7 +61,7 @@ mature.
Usage
-----

There are two ways to use the `py2deb` package: As the command line program
There are two ways to use the py2deb_ package: As the command line program
``py2deb`` and as a Python API. For details about the Python API please refer
to the API documentation hosted on `Read the Docs`_. The command line interface
is described below.
Expand Down Expand Up @@ -166,25 +166,64 @@ So the "--" marker separates the py2deb options from the pip options.
Future improvements
-------------------

Some random ideas for possible improvements to py2deb (in no specific order):
The following sections list possible improvements to the project:

.. contents::
:local:

.. _Python 3.8+ compatibility:

Python 3.8+ compatibility
~~~~~~~~~~~~~~~~~~~~~~~~~

The py2deb_ project builds on top of pip-accel_, which was developed between
2013 and 2015 on top of ``pip >= 7.0, < 7.2``. Since that time pip_ has grown
enormously: At the time of writing (in August 2020) we're now at pip 20!

None of the improvements made between pip 7-20 are available in pip-accel and
py2deb and this has become somewhat of a glaring issue that plenty of users
have run into (see `#17`_, `#18`_, `#27`_ and `#31`_).

Known issues being caused by this include:

- The old pip version prevents Python 3.8+ compatibility.

- The old pip version doesn't know about ``python_requires`` metadata provided
by PyPI and this forces users to maintain constraints files themselves, even
though this shouldn't be necessary.

- While pip-accel supports installation from wheels, it was never exposed via
the Python API and so py2deb lacks support for converting wheels (it
currently needs source distributions).

The current state of affairs is best summarized in `this comment`_. I'm hoping
to complete the upgrade to newer pip and pip-accel releases in the coming weeks
(as of this writing in August 2020) but can't commit to a date.

- Find a way to facilitate (explicit / opt-in) installation of system wide
files (not related to Python per se) based on a Python distribution? This
could significantly reduce the need for "wrapper packages" that basically
just pull in packages converted by py2deb and drop a few configuration files
into place.
.. _this comment: https://github.com/paylogic/py2deb/issues/18#issuecomment-633848582

- Investigate the feasability of supporting conversion of binary wheels. Slowly
but surely the Python community seems to be gravitating towards (binary)
wheels and once gravity has shifted we don't want to be left in the dust! ;-)
Installation of system wide files
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- Make it possible to "replace" Python requirements in a requirement set with a
Debian package that's included in the official repositories (e.g. Pillow_
becomes python-imaging_ or python-pil_). There are some hairy details
involved here.
Find a way to facilitate (explicit / opt-in) installation of system wide files
(not related to Python per se) based on a Python distribution? This could
significantly reduce the need for "wrapper packages" that basically just pull
in packages converted by py2deb and drop a few configuration files into place.

- Dive into PEP-440_ and see if there is a way to fully support it? Then `this
question on Reddit`_ can finally get a satisfying answer :-).
:Related issues: See issue `#7`_ for a related discussion.

Conversion of binary wheels
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Investigate the feasability of supporting conversion of binary wheels. Slowly
but surely the Python community seems to be gravitating towards (binary) wheels
and once gravity has shifted we don't want to be left in the dust! 😉

Full PEP-440 compatibility
~~~~~~~~~~~~~~~~~~~~~~~~~~

Dive into PEP-440_ and see if it can be fully supported? Then `this question on
Reddit`_ can finally get a satisfying answer 🙂.

Similar projects
----------------
Expand All @@ -196,7 +235,7 @@ fairly `detailed comparison`_ with each of these projects.
Contact
-------

The latest version of `py2deb` is available on PyPI_ and GitHub_. The
The latest version of py2deb is available on PyPI_ and GitHub_. The
documentation is hosted on `Read the Docs`_ and includes a changelog_. For
questions, bug reports, suggestions, etc. please create an issue on GitHub_.

Expand All @@ -208,23 +247,30 @@ This software is licensed under the `MIT license`_.
© 2020 Peter Odding, Arjan Verwer and Paylogic International.

.. External references:
.. _changelog: https://py2deb.readthedocs.io/en/latest/changelog.html
.. _CPython: https://en.wikipedia.org/wiki/CPython
.. _deb-pkg-tools: https://pypi.org/project/deb-pkg-tools
.. _detailed comparison: https://py2deb.readthedocs.io/en/latest/comparisons.html
.. _dh-virtualenv: https://github.com/spotify/dh-virtualenv
.. _fpm: https://github.com/jordansissel/fpm
.. _GitHub: https://github.com/paylogic/py2deb
.. _Lintian: http://en.wikipedia.org/wiki/Lintian
.. _MIT license: http://en.wikipedia.org/wiki/MIT_License
.. _PEP-440: https://www.python.org/dev/peps/pep-0440/
.. _Pillow: https://python-pillow.github.io/
.. _pip-accel: https://github.com/paylogic/pip-accel
.. _PyPI: https://pypi.org/project/py2deb
.. _PyPy: https://en.wikipedia.org/wiki/PyPy
.. _Read The Docs: https://py2deb.readthedocs.io
.. _changelog: https://py2deb.readthedocs.io/en/latest/changelog.html
.. _deb-pkg-tools: https://pypi.org/project/deb-pkg-tools
.. _detailed comparison: https://py2deb.readthedocs.io/en/latest/comparisons.html
.. _dh-virtualenv: https://github.com/spotify/dh-virtualenv
.. _fpm: https://github.com/jordansissel/fpm
.. _pip-accel: https://pypi.org/project/pip-accel
.. _pip: https://pypi.org/project/pip
.. _py2deb: https://pypi.org/project/py2deb
.. _python-imaging: https://packages.debian.org/search?keywords=python-imaging
.. _python-pil: https://packages.debian.org/search?keywords=python-pil
.. _Read The Docs: https://py2deb.readthedocs.io
.. _requirement files: http://www.pip-installer.org/en/latest/cookbook.html#requirements-files
.. _stdeb: https://pypi.org/project/stdeb
.. _this question on Reddit: https://www.reddit.com/r/Python/comments/2x7s17/py2deb_python_to_debian_package_converter/coxyyzu
.. _#7: https://github.com/paylogic/py2deb/issues/7
.. _#17: https://github.com/paylogic/py2deb/issues/17
.. _#18: https://github.com/paylogic/py2deb/issues/18
.. _#27: https://github.com/paylogic/py2deb/issues/27
.. _#31: https://github.com/paylogic/py2deb/issues/31

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