sexp 1.1.1

A minimal-allocation S-expression library for Python, backed by a C extension.

sexp

A minimal-allocation S-expression library for Python, backed by a C extension.

Parsing and tree manipulation are handled entirely in C with a bump-pointer arena allocator and an interned string pool. Python gets lightweight node views — no copying, no per-node heap allocation.

Installation

pip install sexp

Requires Python 3.10+. Wheels are provided for Linux (x86_64 + aarch64), macOS (x86_64 + arm64), and Windows (AMD64).

Quick start

from sexp import parse

tree = parse("(define (square x) (* x x))")

tree[0].value         # 'define'
tree[1][0].value      # 'square'
tree.head.value       # 'define'

for node in tree:
    print(node)

src = "(a (b (c d)) e)"
assert repr(parse(src)) == src

Further reading

Path	Contents
CHANGELOG.md	Release history
docs/api.md	Full API reference, including recipes for common patterns
docs/how-it-works.md	Architecture overview: node array, arena, intern pool, parser
docs/internals/	Internals wiki: node array, arena, intern pool, parser, mutation

Development

Prerequisites

Audience	Requirements
Installing from PyPI	Python 3.10+ — wheels are provided for Linux (x86_64, aarch64), macOS (x86_64, arm64), and Windows (AMD64). No compiler needed.
Building from source	Python 3.10+, CMake 3.15+, and a C11 compiler (gcc or clang on Linux/macOS; MSVC 2019+ or clang-cl on Windows).

Setup

python -m venv .venv && source .venv/bin/activate  # Windows: .venv\Scripts\activate
pip install -e '.[dev]'

Running tests

# Python tests
pytest tests/python

# C tests
cmake -B build && cmake --build build
ctest --test-dir build --output-on-failure

# Benchmarks (local only)
pytest benchmarks/ --benchmark-only

License

MIT