=============================
``Python`` Python interpreter
=============================

This guide explains how to run Python on NuttX.

*Yes, you heard it right*. **Python on NuttX**. This is a port of the `CPython <https://github.com/python/cpython>`_ repository for NuttX.
The `CPython` repository is the reference implementation of the Python programming language.
It is written in C and is the most widely used Python interpreter.

.. warning::
   Python for NuttX is still in the experimental stage (thus, it requires ``CONFIG_EXPERIMENTAL`` to be enabled)
   It is not fully functional for all the architectures and configurations.
   Please check this `issue <https://github.com/apache/nuttx-apps/issues/2884>`_ in the `nuttx-apps <https://github.com/apache/nuttx-apps/>`_ repository to know the current status.

How Does it Work?
=================

1. Python for NuttX target initially the ``rv-virt`` (RISC-V QEMU) board.
2. Python modules are stored in `pyc <https://docs.python.org/3/glossary.html#term-bytecode>`_ (byte-code format) and are loaded from a ROMFS image at startup.
3. Environment variables like ``PYTHONHOME`` and ``PYTHON_BASIC_REPL`` need to be set accordingly.

Building Python NuttX
=====================

Use the ``rv-virt:python`` config to build Python for NuttX. Note that the CMake scripts don't work for this configuration. For now, please use the makefile build instead:

.. code:: console

   $ cd nuttx
   $ make distclean
   $ ./tools/configure.sh rv-virt:python
   $ make -j$(nproc)
   $ ls -l nuttx

This will generate a ``nutxx`` binary. This file can be run using the RISC-V QEMU.

Try Python in NSH
=================

.. code:: console

   $ .qemu-system-riscv32 -semihosting -M virt,aclint=on -cpu rv32 -smp 1 -bios none -kernel nuttx -nographic

   ABC
   NuttShell (NSH) NuttX-10.4.0
   nsh> mount_modules
   Mounting ROMFS filesystem at target=/usr/local/lib/ with source=/dev/ram1
   nsh> export PYTHONHOME /usr/local
   nsh> export PYTHON_BASIC_REPL 1
   nsh> python
   Python 3.13.0 (main, Dec  4 2024, 17:00:42) [GCC 13.2.0] on nuttx
   Type "help", "copyright", "credits" or "license" for more information.
   >>>

Demo
----

Check the following `asciinema <https://asciinema.org/>`_ demo to see how to run Python on NuttX. You can copy and paste the commands from the demo to try it yourself.

.. image:: https://asciinema.org/a/orkD8fKuahMEgQfBak9abliE4.svg
   :target: https://asciinema.org/a/orkD8fKuahMEgQfBak9abliE4