PEP: 720
Title: Cross-compiling Python packages
Author: Filipe Laíns <lains@riseup.net>
PEP-Delegate:
Status: Draft
Type: Informational
Content-Type: text/x-rst
Created: 01-Jul-2023
Python-Version: 3.12


Abstract
========

This PEP attempts to document the status of cross-compilation of downstream
projects.

It should give an overview of the approaches currently used by distributors
(Linux distros, WASM environment providers, etc.) to cross-compile downstream
projects (3rd party extensions, etc.).


Motivation
==========

We write this PEP to express the challenges in cross-compilation and act as a
supporting document in future improvement proposals.


Analysis
========


Introduction
------------

There are a couple different approaches being used to tackle this, with
different levels of interaction required from the user, but they all require a
significant amount of effort. This is due to the lack of standardized
cross-compilation infrastructure on the Python packaging ecosystem, which itself
stems from the complexity of cross-builds, making it a huge undertaking.


Upstream support
----------------

Some major projects like CPython, setuptools, etc. provide some support to help
with cross-compilation, but it's unofficial and at a best-effort basis. For
example, the ``sysconfig`` module allows overwriting the data module name via
the ``_PYTHON_SYSCONFIGDATA_NAME`` environment variable, something that is
required for cross-builds, and setuptools `accepts patches`__ [1]_ to tweak/fix
its logic to be compatible with popular `"environment faking"
<faking the target environment_>`_ workflows [2]_.

The lack of first-party support in upstream projects leads to cross-compilation
being fragile and requiring a significant effort from users, but at the same
time, the lack of standardization makes it harder for upstreams to improve
support as there's no clarity on how this feature should be provided.

.. [1] At the time of writing (Jun 2023), setuptools' compiler interface code,
       the component that most of affects cross-compilation, is developed on the
       `pypa/distutils`__ repository, which gets periodically synced to the
       setuptools repository.

.. [2] We specifically mention *popular* workflows, because this is not
       standardized. Though, many of the most popular implementations
       (crossenv_, conda-forge_'s build system, etc.) work similarly, and this
       is what we are referring to here. For clarity, the implementations we are
       referring to here could be described as *crossenv-style*.

.. __: https://github.com/pypa/distutils/pulls?q=cross
.. __: https://github.com/pypa/distutils

Projects with decent cross-build support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It seems relevant to point out that there are a few modern Python package
build-backends with, at least, decent cross-compilation support, those being
scikit-build__ and meson-python__. Both these projects integrate external mature
build-systems into Python packaging — CMake__ and Meson__, respectively — so
cross-build support is inherited from them.

.. __: https://github.com/scikit-build/scikit-build
.. __: https://github.com/mesonbuild/meson-python
.. __: https://cmake.org/
.. __: https://mesonbuild.com/


Downstream approaches
---------------------

Cross-compilation approaches fall in a spectrum that goes from, by design,
requiring extensive user interaction to (ideally) almost none. Usually, they'll
be based on one of two main strategies, using a `cross-build environment`_,
or `faking the target environment`_.

.. _approach-cross-environment:

Cross-build environment
~~~~~~~~~~~~~~~~~~~~~~~

This consists of running the Python interpreter normally and utilizing the
cross-build provided by the projects' build-system. However, as we saw above,
upstream support is lacking, so this approach only works for a small-ish set of
projects. When this fails, the usual strategy is to patch the build-system code
to build use the correct toolchain, system details, etc. [3]_.

Since this approach often requires package-specific patching, it requires a lot
of user interaction.

.. admonition:: Examples
   :class: note

   `python-for-android`_, `kivy-ios`_, etc.

.. [3] The scope of the build-system patching varies between users and usually
       depends on the their goal — some (eg. Linux distributions) may patch the
       build-system to support cross-builds, while others might hardcode
       compiler paths and system information in the build-system, to simply make
       the build work.

Faking the target environment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Aiming to drop the requirement for user input, a popular approach is trying to
fake the target environment. It generally consists of monkeypatching the Python
interpreter to get it to mimic the interpreter on the target system, which
constitutes of changing many of the ``sys`` module attributes, the ``sysconfig``
data, etc. Using this strategy, build-backends do not need to have any
cross-build support, and should just work without any code changes.

Unfortunately, though, it isn't possible to truly fake the target environment.
There are many reasons for this, one of the main ones being that it breaks code
that actually needs to introspect the running interpreter. As a result,
monkeypatching Python to look like target is very tricky — to achieve the less
amount of breakage, we can only patch certain aspects of the interpreter.
Consequently, build-backends may need some code changes, but these are generally
much smaller than the previous approach. This is an inherent limitation of the
technique, meaning this strategy still requires some user interaction.

Nonetheless, this strategy still works out-of-the-box with significantly more
projects than the approach above, and requires much less effort in these cases.
It is successful in decreasing the amount of user interaction needed, even
though it doesn't succeed in being generic.

.. admonition:: Examples
   :class: note

   `crossenv`_, `conda-forge`_, etc.


Environment introspection
-------------------------

As explained above, most build system code is written with the assumption that
the target system is the same as where the build is occurring, so introspection
is usually used to guide the build.

In this section, we try to document most of the ways this is accomplished. It
should give a decent overview of of environment details that are required by
build systems.

.. list-table::
   :header-rows: 1

   *  - Snippet
      - Description
      - Variance

   *  - .. code-block:: python

            >>> importlib.machinery.EXTENSION_SUFFIXES
            [
               '.cpython-311-x86_64-linux-gnu.so',
               '.abi3.so',
               '.so',
            ]

      - Extension (native module) suffixes supported by this interpreter.
      - This is implementation-defined, but it **usually** differs based on the
        implementation, system architecture, build configuration, Python
        language version, and implementation version — if one exists.

   *  - .. code-block:: python

            >>> importlib.machinery.SOURCE_SUFFIXES
            ['.py']

      - Source (pure-Python) suffixes supported by this interpreter.
      - This is implementation-defined, but it **usually** doesn't differ
        (outside exotic implementations or systems).

   *  - .. code-block:: python

            >>> importlib.machinery.all_suffixes()
            [
               '.py',
               '.pyc',
               '.cpython-311-x86_64-linux-gnu.so',
               '.abi3.so',
               '.so',
            ]

      - All module file suffixes supported by this interpreter. It *should* be the
        union of all ``importlib.machinery.*_SUFFIXES`` attributes.
      - This is implementation-defined, but it **usually** differs based on the
        implementation, system architecture, build configuration, Python
        language version, and implementation version — if one exists. See the
        entries above for more information.

   *  - .. code-block:: python

            >>> sys.abiflags
            ''

      - ABI flags, as specified in :pep:`3149`.
      - Differs based on the build configuration.

   *  - .. code-block:: python

            >>> sys.api_version
            1013

      - C API version.
      - Differs based on the Python installation.

   *  - .. code-block:: python

            >>> sys.base_prefix
            /usr

      - Prefix of the installation-wide directories where platform independent
        files are installed.
      - Differs based on the platform, and installation.

   *  - .. code-block:: python

            >>> sys.base_exec_prefix
            /usr

      - Prefix of the installation-wide directories where platform dependent
        files are installed.
      - Differs based on the platform, and installation.

   *  - .. code-block:: python

            >>> sys.byteorder
            'little'

      - Native byte order.
      - Differs based on the platform.

   *  - .. code-block:: python

            >>> sys.builtin_module_names
            ('_abc', '_ast', '_codecs', ...)

      - Names of all modules that are compiled into the Python interpreter.
      - Differs based on the platform, system architecture, and build
        configuration.

   *  - .. code-block:: python

            >>> sys.exec_prefix
            /usr

      - Prefix of the site-specific directories where platform independent files
        are installed. Because it concerns the site-specific directories, in
        standard virtual environment implementation, it will be a
        virtual-environment-specific path.
      - Differs based on the platform, installation, and environment.

   *  - .. code-block:: python

            >>> sys.executable
            '/usr/bin/python'

      - Path of the Python interpreter being used.
      - Differs based on the installation.

   *  - .. code-block:: python

            >>> with open(sys.executable, 'rb') as f:
            ...   header = f.read(4)
            ...   if is_elf := (header == b'\x7fELF'):
            ...     elf_class = int(f.read(1))
            ...     size = {1: 52, 2: 64}.get(elf_class)
            ...     elf_header = f.read(size - 5)

      - Whether the Python interpreter is an ELF file, and the ELF header. This
        approach is something used to identify the target architecture of the
        installation (example__).
      - Differs based on the installation.

   *  - .. code-block:: python

            >>> sys.float_info
            sys.float_info(
               max=1.7976931348623157e+308,
               max_exp=1024,
               max_10_exp=308,
               min=2.2250738585072014e-308,
               min_exp=-1021,
               min_10_exp=-307,
               dig=15,
               mant_dig=53,
               epsilon=2.220446049250313e-16,
               radix=2,
               rounds=1,
            )

      - Low level information about the float type, as defined by ``float.h``.
      - Differs based on the architecture, and platform.

   *  - .. code-block:: python

            >>> sys.getandroidapilevel()
            21

      - Integer representing the Android API level.
      - Differs based on the platform.

   *  - .. code-block:: python

            >>> sys.getwindowsversion()
            sys.getwindowsversion(
               major=10,
               minor=0,
               build=19045,
               platform=2,
               service_pack='',
            )

      - Windows version of the system.
      - Differs based on the platform.

   *  - .. code-block:: python

            >>> sys.hexversion
            0x30b03f0

      - Python version encoded as an integer.
      - Differs based on the Python language version.

   *  - .. code-block:: python

            >>> sys.implementation
            namespace(
               name='cpython',
               cache_tag='cpython-311',
               version=sys.version_info(
                  major=3,
                  minor=11,
                  micro=3,
                  releaselevel='final',
                  serial=0,
               ),
               hexversion=0x30b03f0,
               _multiarch='x86_64-linux-gnu',
            )

      - Interpreter implementation details.
      - Differs based on the interpreter implementation, Python language
        version, and implementation version — if one exists. It may also include
        architecture-dependent information, so it may also differ based on the
        system architecture.

   *  - .. code-block:: python

            >>> sys.int_info
            sys.int_info(
               bits_per_digit=30,
               sizeof_digit=4,
               default_max_str_digits=4300,
               str_digits_check_threshold=640,
            )

      - Low level information about Python's internal integer representation.
      - Differs based on the architecture, platform, implementation, build, and
        runtime flags.

   *  - .. code-block:: python

            >>> sys.maxsize
            0x7fffffffffffffff

      - Maximum value a variable of type ``Py_ssize_t`` can take.
      - Differs based on the architecture, platform, and implementation.

   *  - .. code-block:: python

            >>> sys.maxunicode
            0x10ffff

      - Value of the largest Unicode code point.
      - Differs based on the implementation, and on Python versions older than
        3.3, the build.

   *  - .. code-block:: python

            >>> sys.platform
            linux

      - Platform identifier.
      - Differs based on the platform.

   *  - .. code-block:: python

            >>> sys.prefix
            /usr

      - Prefix of the site-specific directories where platform dependent files
        are installed. Because it concerns the site-specific directories, in
        standard virtual environment implementation, it will be a
        virtual-environment-specific path.
      - Differs based on the platform, installation, and environment.

   *  - .. code-block:: python

            >>> sys.platlibdir
            lib

      - Platform-specific library directory.
      - Differs based on the platform, and vendor.

   *  - .. code-block:: python

            >>> sys.version_info
            sys.version_info(
               major=3,
               minor=11,
               micro=3,
               releaselevel='final',
               serial=0,
            )

      - Python language version implemented by the interpreter.
      - Differs if the target Python version is not the same [4]_.

   *  - .. code-block:: python

            >>> sys.thread_info
            sys.thread_info(
               name='pthread',
               lock='semaphore',
               version='NPTL 2.37',
            )

      - Information about the thread implementation.
      - Differs based on the platform, and implementation.

   *  - .. code-block:: python

            >>> sys.winver
            3.8-32

      - Version number used to form Windows registry keys.
      - Differs based on the platform, and implementation.

   *  - .. code-block:: python

         >>> sysconfig.get_config_vars()
         { ... }
         >>> sysconfig.get_config_var(...)
         ...

      - Python distribution configuration variables. It includes a set of
        variables [5]_ — like ``prefix``, ``exec_prefix``, etc. — based on the
        running context [6]_, and may include some extra variables based on the
        Python implementation and system.

        In CPython and most other implementations that use the same
        build-system, the "extra" variables mention above are: on POSIX, all
        variables from the ``Makefile`` used to build the interpreter, and on
        Windows, it usually only includes a small subset of the those [7]_ —
        like ``EXT_SUFFIX``, ``BINDIR``, etc.

      - This is implementation-defined, but it **usually** differs between
        non-identical builds. Please refer to the
        `sysconfig configuration variables`_ table for a overview of the different
        configuration variable that are usually present.

.. [4] Ideally, you want to perform cross-builds with the same Python version
       and implementation, however, this is often not the case. It should not
       be very problematic as long as the major and minor versions don't
       change.

.. [5] The set of config variables that will always be present mostly consists
       of variables needed to calculate the installation scheme paths.

.. [6] The context we refer here consists of the "path initialization", which is
       a process that happens in the interpreter startup and is responsible for
       figuring out which environment it is being run — eg. global environment,
       virtual environment, etc. — and setting ``sys.prefix`` and other
       attributes accordingly.

.. [7] This is because Windows builds may not use the ``Makefile``, and instead
       `use the Visual Studio build system`__. A subset of the most relevant
       ``Makefile`` variables is provided to make user code that uses them
       simpler.

.. __: https://github.com/pypa/packaging/blob/2f80de7fd2a8bc199dadf5cf3f5f302a17084792/src/packaging/_manylinux.py#L43-L50
.. __: https://docs.python.org/3/using/configure.html#debug-build


CPython (and similar)
~~~~~~~~~~~~~~~~~~~~~


.. list-table:: ``sysconfig`` configuration variables
   :name: sysconfig configuration variables
   :header-rows: 1
   :widths: 20 20 30 30

   *  - Name
      - Example Value
      - Description
      - Variance

   *  - ``SOABI``
      - ``cpython-311-x86_64-linux-gnu``
      - ABI string — defined by :pep:`3149`.
      - Differs based on the implementation, system architecture, Python
        language version, and implementation version — if one exists.

   *  - ``SHLIB_SUFFIX``
      - ``.so``
      - Shared library suffix.
      - Differs based on the platform.

   *  - ``EXT_SUFFIX``
      - ``.cpython-311-x86_64-linux-gnu.so``
      - Interpreter-specific Python extension (native module) suffix — generally
        defined as ``.{SOABI}.{SHLIB_SUFFIX}``.
      - Differs based on the implementation, system architecture, Python
        language version, and implementation version — if one exists.

   *  - ``LDLIBRARY``
      - ``libpython3.11.so``
      - Shared ``libpython`` library name — if available. If unavailable [8]_,
        the variable will be empty, if available, the library should be located
        in ``LIBDIR``.
      - Differs based on the implementation, system architecture, build
        configuration, Python language version, and implementation version — if
        one exists.

   *  - ``PY3LIBRARY``
      - ``libpython3.so``
      - Shared Python 3 only (major version bound only) [9]_ ``libpython``
        library name — if available. If unavailable [8]_, the variable will be
        empty, if available, the library should be located in ``LIBDIR``.
      - Differs based on the implementation, system architecture, build
        configuration, Python language version, and implementation version — if
        one exists.

   *  - ``LIBRARY``
      - ``libpython3.11.a``
      - Static ``libpython`` library name — if available. If unavailable [8]_,
        the variable will be empty, if available, the library should be located
        in ``LIBDIR``.
      - Differs based on the implementation, system architecture, build
        configuration, Python language version, and implementation version — if
        one exists.

   *  - ``Py_DEBUG``
      - ``0``
      - Whether this is a `debug build`__.
      - Differs based on the build configuration.

   *  - ``WITH_PYMALLOC``
      - ``1``
      - Whether this build has pymalloc__ support.
      - Differs based on the build configuration.

   *  - ``Py_TRACE_REFS``
      - ``0``
      - Whether reference tracing (debug build only) is enabled.
      - Differs based on the build configuration.

   *  - ``Py_UNICODE_SIZE``
      -
      - Size of the ``Py_UNICODE`` object, in bytes. This variable is only
        present in CPython versions older than 3.3, and was commonly used to
        detect if the build uses UCS2 or UCS4 for unicode objects — before
        :pep:`393`.
      - Differs based on the build configuration.

   *  - ``Py_ENABLE_SHARED``
      - ``1``
      - Whether a shared ``libpython`` is available.
      - Differs based on the build configuration.

   *  - ``PY_ENABLE_SHARED``
      - ``1``
      - Whether a shared ``libpython`` is available.
      - Differs based on the build configuration.

   *  - ``CC``
      - ``gcc``
      - The C compiler used to build the Python distribution.
      - Differs based on the build configuration.

   *  - ``CXX``
      - ``g++``
      - The C compiler used to build the Python distribution.
      - Differs based on the build configuration.

   *  - ``CFLAGS``
      - ``-DNDEBUG -g -fwrapv ...``
      - The C compiler flags used to build the Python distribution.
      - Differs based on the build configuration.

   *  - ``py_version``
      - ``3.11.3``
      - Full form of the Python version.
      - Differs based on the Python language version.

   *  - ``py_version_short``
      - ``3.11``
      - Custom form of the Python version, containing only the major and minor
        numbers.
      - Differs based on the Python language version.

   *  - ``py_version_nodot``
      - ``311``
      - Custom form of the Python version, containing only the major and minor
        numbers, and no dots.
      - Differs based on the Python language version.

   *  - ``prefix``
      - ``/usr``
      - Same as ``sys.prefix``, please refer to the entry in table above.
      - Differs based on the platform, installation, and environment.

   *  - ``base``
      - ``/usr``
      - Same as ``sys.prefix``, please refer to the entry in table above.
      - Differs based on the platform, installation, and environment.

   *  - ``exec_prefix``
      - ``/usr``
      - Same as ``sys.exec_prefix``, please refer to the entry in table above.
      - Differs based on the platform, installation, and environment.

   *  - ``platbase``
      - ``/usr``
      - Same as ``sys.exec_prefix``, please refer to the entry in table above.
      - Differs based on the platform, installation, and environment.

   *  - ``installed_base``
      - ``/usr``
      - Same as ``sys.base_prefix``, please refer to the entry in table above.
      - Differs based on the platform, and installation.

   *  - ``installed_platbase``
      - ``/usr``
      - Same as ``sys.base_exec_prefix``, please refer to the entry in table
        above.
      - Differs based on the platform, and installation.

   *  - ``platlibdir``
      - ``lib``
      - Same as ``sys.platlibdir``, please refer to the entry in table above.
      - Differs based on the platform, and vendor.

   *  - ``SIZEOF_*``
      - ``4``
      - Size of a certain C type (``double``, ``float``, etc.).
      - Differs based on the system architecture, and build details.


.. [8] Due to Python bring compiled without shared or static ``libpython``
       support, respectively.

.. [9] This is the ``libpython`` library that users of the `stable ABI`__ should
       link against, if they need to link against ``libpython``.

.. __: https://docs.python.org/3/c-api/intro.html#debugging-builds
.. __: https://docs.python.org/3/c-api/memory.html#pymalloc
.. __: https://docs.python.org/3/c-api/stable.html#stable-application-binary-interface


Relevant Information
--------------------

There are some bits of information required by build systems — eg. platform
particularities — scattered across many places, and it often is difficult to
identify code with assumptions based on them. In this section, we try to
document the most relevant cases.


When should extensions be linked against ``libpython``?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Short answer
   Yes, on Windows. No on POSIX platforms, except Android, Cygwin, and other
   Windows-based POSIX-like platforms.

When building extensions for dynamic loading, depending on the target platform,
they may need to be linked against ``libpython``.

On Windows, extensions need to link against ``libpython``, because all symbols
must be resolvable at link time. POSIX-like platforms based on Windows — like
Cygwin, MinGW, or MSYS — will also require linking against ``libpython``.

On most POSIX platforms, it is not necessary to link against ``libpython``, as
the symbols will already be available in the due to the interpreter — or, when
embedding, the executable/library in question — already linking to
``libpython``. Not linking an extension module against ``libpython`` will allow
it to be loaded by static Python builds, so when possible, it is desirable to do
so (see GH-65735__).

This might not be the case on all POSIX platforms, so make sure you check. One
example is Android, where only the main executable and ``LD_PRELOAD`` entries
are considered to be ``RTLD_GLOBAL`` (meaning dependencies are ``RTLD_LOCAL``)
[10]_, which causes the ``libpython`` symbols be unavailable when loading the
extension.

.. [10] Refer to `dlopen's man page`__ for more information.

.. __: https://github.com/python/cpython/issues/65735
.. __: https://man.archlinux.org/man/dlopen.3


What are ``prefix``, ``exec_prefix``, ``base_prefix``, and ``base_exec_prefix``?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These are ``sys`` attributes `set in the Python initialization`__ that describe
the running environment. They refer to the prefix of directories where
installation/environment files are installed, according to the table below.

==================== ====================================== =================
Name                 Target files                           Environment Scope
==================== ====================================== =================
``prefix``           platform independent (eg. pure Python) site-specific
``exec_prefix``      platform dependent (eg. native code)   site-specific
``base_prefix``      platform independent (eg. pure Python) installation-wide
``base_exec_prefix`` platform dependent (eg. native code)   installation-wide
==================== ====================================== =================

Because the site-specific prefixes will be different inside virtual
environments, checking ``sys.prexix != sys.base_prefix`` is commonly used to
check if we are in a virtual environment.

.. __: https://github.com/python/cpython/blob/6a70edf24ca217c5ed4a556d0df5748fc775c762/Modules/getpath.py

Case studies
============


crossenv
--------

:Description: Virtual Environments for Cross-Compiling Python Extension Modules.
:URL: https://github.com/benfogle/crossenv

``crossenv`` is a tool to create a virtual environment with a monkeypatched
Python installation that tries to emulate the target machine in certain
scenarios. More about this approach can be found in the
`Faking the target environment`_ section.


conda-forge
-----------

:Description: A community-led collection of recipes, build infrastructure and distributions for the conda package manager.
:URL: https://conda-forge.org/

XXX: Jaime will write a quick summary once the PEP draft is public.

XXX
Uses a modified crossenv.


Yocto Project
-------------

:Description:  The Yocto Project is an open source collaboration project that helps developers create custom Linux-based systems regardless of the hardware architecture.
:URL: https://www.yoctoproject.org/

XXX: Sent email to the mailing list.

TODO


Buildroot
---------

:Description: Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation.
:URL: https://buildroot.org/

TODO


Pyodide
-------

:Description: Pyodide is a Python distribution for the browser and Node.js based on WebAssembly.
:URL: https://pyodide.org/en/stable/

XXX: Hood should review/expand this section.

``Pyodide`` is a provides a Python distribution compiled to WebAssembly__
using the Emscripten__ toolchain.

It patches several aspects of the CPython installation and some external
components. A custom package manager — micropip__ — supporting both Pure and
wasm32/Emscripten wheels, is also provided as a part of the distribution. On top
of this, a repo with a `selected set of 3rd party packages`__ is also provided
and enabled by default.

.. __: https://webassembly.org/
.. __: https://emscripten.org/
.. __: https://micropip.pyodide.org/
.. __: https://pyodide.org/en/stable/usage/packages-in-pyodide.html


Beeware
-------

:Description: BeeWare allows you to write your app in Python and release it on multiple platforms.
:URL: https://beeware.org/

TODO


python-for-android
------------------

:Description: Turn your Python application into an Android APK.
:URL: https://github.com/kivy/python-for-android

resource https://github.com/Android-for-Python/Android-for-Python-Users

``python-for-android`` is a tool to package Python apps on Android. It creates a
Python distribution with your app and its dependencies.

Pure-Python dependencies are handled automatically and in a generic way, but
native dependencies need recipes__. A set of recipes for
`popular dependencies`__ is provided, but users need to provide their own
recipes for any other native dependencies.

.. __: https://python-for-android.readthedocs.io/en/latest/recipes/
.. __: https://github.com/kivy/python-for-android/tree/develop/pythonforandroid/recipes


kivy-ios
--------

:Description:  Toolchain for compiling Python / Kivy / other libraries for iOS.
:URL: https://github.com/kivy/kivy-ios

``kivy-ios`` is a tool to package Python apps on iOS. It provides a toolchain to
build a Python distribution with your app and its dependencies, as well as a CLI
to create and manage Xcode projects that integrate with the toolchain.

It uses the same approach as `python-for-android`_ (also maintained by the
`Kivy project`__) for app dependencies — pure-Python dependencies are handled
automatically, but native dependencies need recipes__, and the project provides
recipes for `popular dependencies`__.

.. __: https://kivy.org
.. __: https://python-for-android.readthedocs.io/en/latest/recipes/
.. __: https://github.com/kivy/kivy-ios/tree/master/kivy_ios/recipes


AidLearning
-----------

:Description: AI, Android, Linux, ARM: AI application development platform based on Android+Linux integrated ecology.
:URL: https://github.com/aidlearning/AidLearning-FrameWork

TODO


QPython
-------

:Description: QPython is the Python engine for android.
:URL: https://github.com/qpython-android/qpython

TODO


pyqtdeploy
----------

:Description: pyqtdeploy is a tool for deploying PyQt applications.
:URL: https://www.riverbankcomputing.com/software/pyqtdeploy/

contact https://www.riverbankcomputing.com/pipermail/pyqt/2023-May/thread.html
contacted Phil, the maintainer

TODO


Chaquopy
--------

:Description: Chaquopy provides everything you need to include Python components in an Android app.
:URL: https://chaquo.com/chaquopy/

TODO


EDK II
------

:Description: EDK II is a modern, feature-rich, cross-platform firmware development environment for the UEFI and PI specifications.
:URL: https://github.com/tianocore/edk2-libc/tree/master/AppPkg/Applications/Python

TODO


ActivePython
------------

:Description: Commercial-grade, quality-assured Python distribution focusing on easy installation and cross-platform compatibility on Windows, Linux, Mac OS X, Solaris, HP-UX and AIX.
:URL: https://www.activestate.com/products/python/

TODO


Termux
------

:Description: Termux is an Android terminal emulator and Linux environment app that works directly with no rooting or setup required.
:URL: https://termux.dev/en/

TODO
