---
id: ordered-set
version: "4.1.0"
license: unclear
license_treatment: permissive
maintenance: dormant
---

# ordered-set — An OrderedSet is a custom MutableSet that remembers its order, so that every

License: permissive · Maintenance: dormant · Popularity: top 1,000 on PyPI

## Install

pip install ordered-set
uv add ordered-set
poetry add ordered-set

## Description

[![Pypi](https://img.shields.io/pypi/v/ordered-set.svg)](https://pypi.python.org/pypi/ordered-set)

An OrderedSet is a mutable data structure that is a hybrid of a list and a set.
It remembers the order of its entries, and every entry has an index number that
can be looked up.

## Installation

`ordered_set` is available on PyPI and packaged as a wheel. You can list it
as a dependency of your project, in whatever form that takes.

To install it into your current Python environment:

    pip install ordered-set

To install the code for development, after checking out the repository:

    pip install flit
    flit install

## Usage examples

An OrderedSet is created and used like a set:

    >>> from ordered_set import OrderedSet

    >>> letters = OrderedSet('abracadabra')

    >>> letters
    OrderedSet(['a', 'b', 'r', 'c', 'd'])

    >>> 'r' in letters
    True

It is efficient to find the index of an entry in an OrderedSet, or find an
entry by its index. To help with this use case, the `.add()` method returns
the index of the added item, whether it was already in the set or not.

    >>> letters.index('r')
    2

    >>> letters[2]
    'r'

    >>> letters.add('r')
    2...

## AI interpretation — verify before relying

A mutable set that preserves insertion order and supports index-based access, combining set operations with list-like random lookup and slicing.

Verdict: A lightweight, dependency-free ordered set implementation suitable for production use. Dormant maintenance and a two-year gap since the last release are typical for a stable, feature-complete library, but users should be aware that bug fixes or compatibility updates may be slow. No known vulnerabilities.

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