---
id: regions
version: "0.12"
license: BSD-3-Clause
license_treatment: permissive
maintenance: active
---

# regions — An Astropy coordinated package for region handling

License: permissive · Maintenance: active · Downloads: 118.9K/mo

## What it is and what it does

Regions is an Astropy package that provides a unified interface for working with astronomical regions—geometric shapes defined on the celestial sphere or in pixel coordinates. It handles the creation, manipulation, and analysis of regions commonly used in astronomy workflows. The package integrates tightly with astropy and numpy, allowing astronomers to work with regions in a Pythonic way.

The package is actively maintained as part of the Astropy ecosystem and supports current Python versions. It includes both sky-based regions and pixel-based regions, enabling flexible region handling across different astronomical data types and workflows.

Use it for:

- Define apertures for photometric measurements on astronomical images
- Create masks to exclude or include specific regions when analyzing survey data
- Convert between different region coordinate systems in astronomical workflows
- Store and retrieve region definitions for reproducible astronomical analysis
- Filter astronomical catalogs based on spatial region membership

## Worth the install?

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

Regions provides tools for defining, manipulating, and analyzing astronomical regions—geometric shapes on the sky used in astronomy data analysis.

Yes, if you work with astronomical data and need to define or manipulate spatial regions. The package is actively maintained, has no known vulnerabilities, and integrates with the Astropy ecosystem. The medium install friction is typical for scientific Python packages with compiled dependencies. BSD-3-Clause licensing poses no restrictions for most use cases.

## Install

pip install regions
uv add regions
poetry add regions

## Installing regions

Before you install: Medium install friction due to compiled dependencies. Active maintenance with recent release; last commit was 2026-08-07. Requires Python 3.11 or later.

License in practice: BSD-3-Clause permissive license allows commercial and private use with minimal restrictions, provided the license notice is retained.

Quickstart:

pip install regions

import regions
import numpy
import astropy

# Create a region for astronomical analysis
region = regions.Region()

Requires Python 3.11 or later; astropy and numpy must be installed.

Verify before relying:

- Specific region types supported (circular, elliptical, polygonal, etc.)
- Whether regions can be serialized to/from standard formats (FITS, DS9, etc.)
- Performance characteristics for large region sets or complex geometries
- Concrete usage examples beyond basic region creation

## Package facts

- License: BSD-3-Clause (permissive)
- Python support: supports_current
- Install friction: medium
- Maintenance: active
- Downloads: 118.9K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

astronomical region handling, sky region geometry, astropy regions, celestial coordinate regions, astronomy region masks, pixel region definitions, sky aperture tools, astronomy, astropy-ecosystem, spatial-geometry

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