Contributing guidelines

Contributions are welcome!

Big changes

Please open a new issue to discuss or propose a major change. Not only is it fun to discuss big ideas, but we might save each other’s time too. Perhaps some of the work you’re contemplating is already half-done in a development branch.

Code style: Python

We use PEP8, black for code formatting and isort for import sorting. The settings for these programs are in pyproject.toml and setup.cfg. Pull requests should follow the style guide. One difference we use from “black” style is that strings shown to the user are always in double quotes (") and strings for internal uses are in single quotes (').

Code style: C++

The file .clang-format contains our C++ format based on Clang’s formatter, imperfect as it is. We eagerly await a dangling parenthesis (

In general we prefer to make our C++ look similar to Python PEP8, within reason, because our code is primarily a Python binding. That is, variable and method names are snake_case, class names are CamelCase. Our coding conventions are closer to pybind11’s than QPDF’s. When a C++ object wraps is a Python object, it should follow the Python naming conventions for that type of object, e.g. auto Decimal = py::module_::import("decimal").attr("Decimal") for a reference to the Python Decimal class even though it is a C++ object.

We don’t like the traditional C++ .cpp/.h separation that results in a lot of repetition. Headers that are included by only one .cpp can contain a complete class, and get the -inl.h suffix, unless multiple inclusion is required.

Use RAII. Avoid naked pointers. Use the STL, use std::string instead of char *. Use #pragma once as a header guard rather than silly #ifdef; they have been around for 25 years.


New features should come with tests that confirm their correctness.

New dependencies

If you are proposing a change that will require a new dependency, we prefer dependencies that are already packaged by Debian or Red Hat. This makes life much easier for our downstream package maintainers.

Dependencies must also be compatible with the source code license.

English style guide

pikepdf is always spelled “pikepdf”, and never capitalized even at the beginning of a sentence.

Periodic allusions to fish are required, and the writer shall be energetic and mildly amusing.

Known ports/packagers

pikepdf has been ported to many platforms already. If you are interesting in porting to a new platform, check with Repology to see the status of that platform.