---
id: igwn-ligolw
version: "2.1.1"
license: GPL-3.0-or-later
license_treatment: copyleft
maintenance: aging
---

# igwn-ligolw — Python LIGO Light-Weight XML I/O Library

License: copyleft · Maintenance: aging · Downloads: 98.0K/mo

## What it is and what it does

igwn-ligolw is a Python I/O library for the LIGO Light-Weight XML format, a specialized XML schema used extensively in gravitational-wave astronomy for compact object detection pipelines and associated analysis tools. The package was forked in 2024 from the original python-ligo-lw project and provides core functionality to read, write, and interact with LIGOLW documents programmatically.

The library integrates with standard scientific Python dependencies (numpy, pyyaml, tqdm, python-dateutil) and the igwn-segments package to handle time-interval logic. It is classified as Mature and supports Python 3.9 through 3.14, with prebuilt wheels available for common platforms. The copyleft GPL-3.0-or-later license means any derivative work must remain open-source.

Use it for:

- Parse and extract event data from LIGO detector output XML files in gravitational-wave analysis workflows.
- Serialize detector metadata and pipeline results back to LIGOLW format for archival or downstream tool consumption.
- Integrate LIGOLW document handling into custom compact object detection or parameter estimation pipelines.
- Convert or validate LIGOLW XML schemas as part of data quality or format migration tasks.
- Access and manipulate time-interval metadata stored in LIGOLW documents using igwn-segments integration.

## Worth the install?

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

Reads, writes, and manipulates LIGO Light-Weight XML documents used in gravitational-wave detection pipelines and related scientific analysis.

Yes, if you work with LIGO gravitational-wave data or compact object detection pipelines. The package is mature, actively maintained (last release 207 days ago), has no known vulnerabilities, and provides the standard Python interface for LIGOLW I/O. The copyleft license is a constraint only if you need proprietary distribution. Medium install friction is acceptable for a specialized scientific library with prebuilt wheels.

## Install

pip install igwn-ligolw
uv add igwn-ligolw
poetry add igwn-ligolw

## Installing igwn-ligolw

Before you install: Medium install friction with prebuilt wheels for Python 3.10–3.13 across macOS, Linux, and musl platforms. Last release 207 days ago; marked as aging but classified as Mature. Requires Python ≥3.9.

License in practice: Licensed under GPL-3.0-or-later (copyleft). Any derivative work or bundled distribution must also be open-source under compatible terms; proprietary use requires explicit permission or relicensing.

Quickstart:

pip install igwn-ligolw

import igwn.ligolw

# Load and parse a LIGOLW XML document
doc = igwn.ligolw.load('data.xml')

Requires Python ≥3.9; depends on igwn-segments, numpy, python-dateutil, pyyaml, and tqdm.

Verify before relying:

- Exact API surface and supported LIGOLW schema versions not detailed in excerpt.
- Performance characteristics for large XML documents not specified.
- Whether the fork from python-ligo-lw introduces breaking changes or maintains backward compatibility.

## Package facts

- License: GPL-3.0-or-later (copyleft)
- Python support: supports_current
- Install friction: medium
- Maintenance: aging
- Downloads: 98.0K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

LIGO XML format I/O, gravitational wave data format, compact object detection XML, LIGOLW document parser, scientific XML serialization, gravitational-waves, xml-io, ligo

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