---
id: pcpp
version: "1.30"
license: BSD
license_treatment: permissive
maintenance: aging
---

# pcpp — A C99 preprocessor written in pure Python

License: permissive · Maintenance: aging · Downloads: 791.6K/mo

## What it is and what it does

pcpp is a C99 preprocessor written entirely in Python, designed to handle C and C++ preprocessing tasks at build or packaging time. It processes #include directives, macro definitions, and conditional compilation blocks, and can output either fully expanded code or partially preprocessed code with selective pass-through of certain directives. The package is useful for collapsing header-only C++ libraries into single files, preparing code for documentation tools like Doxygen, or integrating preprocessing into Python-based build pipelines.

The preprocessor passes a modified mcpp unit test suite and handles complex recursive macro expansions that conform to C99 standards. It offers both a Python API (by subclassing the Preprocessor class) and a command-line tool that mimics conventional C preprocessors. Partial preprocessing modes allow fine-grained control over which directives are executed versus passed through, making it flexible for different build scenarios.

Use it for:

- Collapse header-only C++ template libraries into single-file includes for easier distribution
- Preprocess C code before feeding it to documentation generators like Doxygen that have limited preprocessor capabilities
- Expand macros and resolve conditional compilation in C source files as part of a Python-based build system
- Benchmark and analyze header file complexity to identify optimization opportunities in build times
- Selectively expand nested includes while preserving system header references in generated output

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

A pure Python implementation of a C99 preprocessor that can preprocess C/C++ header files and source code, available both as a Python module and command-line tool.

Yes, if you need C99 preprocessing in a Python environment. The package is stable and dependency-free, making it easy to integrate. However, the 2021 release date and aging maintenance status mean it may not track the latest C standards or receive active bug fixes—suitable for established workflows but verify compatibility with your specific C/C++ code patterns first.

## Install

pip install pcpp
uv add pcpp
poetry add pcpp

## Installing pcpp

Before you install: Low install friction with no runtime dependencies. Package is in production/stable status but aging—last release was in 2021, though the repository remains active with recent commits.

License in practice: BSD license (permissive) means you can use, modify, and distribute this package freely in commercial and open-source projects with minimal restrictions.

Quickstart:

pip install pcpp

from pcpp.preprocessor import Preprocessor
prep = Preprocessor()
prep.parse(open('input.h').read())
print(prep.write())

Verify before relying:

- Whether Python 2 support (listed in classifiers) is actively maintained given the 2021 release date
- Current performance characteristics under modern Python versions compared to the stated 0.84x–2.62x range under PyPy

## Package facts

- License: BSD (permissive)
- Python support: unspecified
- Install friction: low
- Maintenance: aging
- Downloads: 791.6K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

C preprocessor Python, C99 preprocessor, header file preprocessing, C macro expansion, build stage preprocessing, single file includes, macro evaluation, c-preprocessing, build-automation, header-processing

[View on SkillFed](https://skillfed.io/packages/pcpp) · [View on PyPI](https://pypi.org/project/pcpp/)