Contributor guide

Development environment

If you’re reading this, you’re probably interested in contributing to pyppmd. Thank you very much! The purpose of this guide is to get you to the point where you can make improvements to the PyPPMd and share them with the rest of the team.

Setup Python and C compiler

The PyPPMd is written in the Python and C languages bound with both CFFI, C Foreign Function Interface, and CPython C/C++ API. CFFI is used for PyPy3 and CPython API is used for CPython.

Python installation for various platforms with various ways. You need to install Python environment which support pip command. Venv/Virtualenv is recommended for development.

We have a test suite with python 3.8 and pypy3. If you want to run all the test with these versions and variant on your local, you should install these versions. You can run test with CI environment on Github actions.

Get Early Feedback

If you are contributing, do not feel the need to sit on your contribution until it is perfectly polished and complete. It helps everyone involved for you to seek feedback as early as you possibly can. Submitting an early, unfinished version of your contribution for feedback in no way prejudices your chances of getting that contribution accepted, and can save you from putting a lot of work into a contribution that is not suitable for the project.

Code Contribution

Steps submitting code

When contributing code, you’ll want to follow this checklist:

  1. Fork the repository on GitHub.

  2. Run the tox tests to confirm they all pass on your system. If they don’t, you’ll need to investigate why they fail. If you’re unable to diagnose this yourself, raise it as a bug report.

  3. Write tests that demonstrate your bug or feature. Ensure that they fail.

  4. Make your change.

  5. Run the entire test suite again using tox, confirming that all tests pass including the ones you just added.

  6. Send a GitHub Pull Request to the main repository’s master branch. GitHub Pull Requests are the expected method of code collaboration on this project.

Code review

Contribution will not be merged until they have been code reviewed. There are limited reviewer in the team, reviews from other contributors are also welcome. You should implemented a review feedback unless you strongly object to it.

Code style

The pyppmd uses the PEP8/Black code style. In addition to the standard PEP8, we have an extended guidelines.

  • line length should not exceed 125 characters.

  • Black format prettier is enforced.

  • It also use MyPy static type check enforcement.

Test cases

There is three types of tests and we measures coverages;

  • Unit tests for encode and decode, single data, and multiple data.

  • Integration test with CSV file which size is larger than buffer size.

  • Hypothesis fuzzing test.

All tests should be passed before merging.

C bindings development

Debuggng bindings has always been itchy task for developers. Even proprietary modern IDEs, such as PyCharm Professional/CLion, does not provide a cross debugging feature. Ref:

PyPpmd project source has a hacky way to do it.


The project has a CMakeLists.txt file to run cross-debugging, CMake is a cross-platform builder meta tool for C/C++ projects. You can run PyPpmd project as a C project using the file.

Jetbrains CLion

CLion is an IDE tool for C/C++ development that support CMake for build configuration. You can use CLion for PyPpmd development.


  • Python 3.8.x

  • python development files (for example python3.8-dev package)

  • venv

  • GCC or CLang C/C++ compiler

  • CMake 3.19 or later

When you want to change target python variation and version, please edit CMakeLists.txt#L8-L9

set(PY_VERSION 3.8)

Manual build and run


mkdir cmake-build
cd cmake-build
cmake ..
make pytest_runner
gdb ./pytest_runner ../tests

pytest_runner is a generated program that help you run pytest under C/C++ debugger. You may want to run it on IDE environment.

You can also run pytest with tox

tox -e py38

Library build

cd cmake-build
make pyppmd

CMake targets and files

THere are several targets you can build.


A C++ program that launch python and pytest. The source code is generated by CMake configuration onto cmake build directory (cmake-build in above example).


A virtual target to produce C extension for CPython.


compile C files into static library file. Just convenient target for compilation.


interim target to produce virtualenv environment for pytest_runner