---
id: sexpdata
version: "1.0.2"
license: BSD 2-Clause License Copyright (c) 2019, Joshua Boyd 'jd-boyd' All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the… (full text in the JSON record)
license_treatment: permissive
maintenance: aging
---

# sexpdata — S-expression parser for Python

License: permissive · Maintenance: aging · Downloads: 139.4K/mo

## What it is and what it does

sexpdata is a lightweight S-expression parser and serializer for Python. It reads Lisp-style symbolic expressions (nested lists and quoted strings) from text and converts them to Python lists and strings, or does the reverse—turning Python data structures back into S-expression text. The API mirrors familiar serialization libraries like `json` and `pickle`, with simple `loads`/`dumps` functions for string data and `load`/`dump` for file I/O.

The package has no runtime dependencies and supports Python 3.7 through 3.12. It is classified as Alpha-stage software and has not seen a release in some time, though the repository remains minimally maintained. Use it when you need to exchange data with Lisp systems, parse configuration files in S-expression format, or work with symbolic data structures in a Python context.

Use it for:

- Parse Lisp or Scheme configuration files and convert them to Python data for processing.
- Serialize Python data structures to S-expression format for exchange with Lisp-based tools.
- Read symbolic expressions from text and manipulate them as nested Python lists.
- Build a bridge between Python and Emacs Lisp or other Lisp dialects for interop.

## Worth the install?

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

Parses and serializes S-expressions (Lisp-style symbolic expressions) to and from Python data structures, providing `load`/`dump` functions similar to `json` or `pickle`.

Yes, if you need S-expression parsing. The package is simple, dependency-free, and permissively licensed. However, be aware that it is aging—no release in 948 days—so if you encounter bugs or need new features, maintenance may be slow. For basic S-expression I/O with stable Python versions, it is a reasonable choice.

## Install

pip install sexpdata
uv add sexpdata
poetry add sexpdata

## Installing sexpdata

Before you install: Low friction installation with no runtime dependencies. Maintenance is aging—last release was 948 days ago, though the repository remains active with a recent commit on 2025-09-18 and 111 stars.

License in practice: BSD 2-Clause License is permissive; you may use, modify, and distribute the package freely in commercial or private projects provided you retain the license notice and disclaimer.

Quickstart:

pip install sexpdata

from sexpdata import loads, dumps
data = loads('("a" "b")')
print(data)  # ['a', 'b']
print(dumps(['a', 'b']))  # ("a" "b")

Verify before relying:

- Whether the parser handles nested or complex S-expressions beyond the simple example shown.
- Performance characteristics or limits for large or deeply nested expressions.
- Whether round-trip fidelity (parse then serialize) is guaranteed for all valid inputs.

## Package facts

- License: BSD 2-Clause License Copyright (c) 2019, Joshua Boyd 'jd-boyd' All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the… (full text in the JSON record) (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: aging
- Downloads: 139.4K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

s-expression parser, lisp parser python, symbolic expression parsing, sexp serializer, lisp data format, s-expr to python, lisp-interop, symbolic-data

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