pyrsistent

Persistent/Functional/Immutable data structures

pyrsistent Permissive license MIT AGING ★ 2,196 v0.20.0 released 2023-10-25

Install

pyrsistent on PyPI

pip

pip install pyrsistent

uv

uv add pyrsistent

poetry

poetry add pyrsistent

Package facts

License	MIT (permissive)
Python support	supports the current Python release (>=3.8)
Install friction	low — pure-Python wheel
Runtime dependencies	none
Maintenance	aging — 1,023 days since the last release
Last repo commit	2026-01-31
First released	2013-11-10
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: pyrsistent-0.20.0-py3-none-any.whl

Intended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: PyPy

About pyrsistent

from the package's own PyPI description — quoted content, verbatim

Pyrsistent

.. image:: https://github.com/tobgu/pyrsistent/actions/workflows/tests.yaml/badge.svg :target: https://github.com/tobgu/pyrsistent/actions/workflows/tests.yaml

.. _Pyrthon: https://www.github.com/tobgu/pyrthon .. _Pyrsistent_extras: https://github.com/mingmingrr/pyrsistent-extras

Pyrsistent is a number of persistent collections (by some referred to as functional data structures). Persistent in the sense that they are immutable.

All methods on a data structure that would normally mutate it instead return a new copy of the structure containing the requested updates. The original structure is left untouched.

This will simplify the reasoning about what a program does since no hidden side effects ever can take place to these data structures. You can rest assured that the object you hold a reference to will remain the same throughout its lifetime and need not worry that somewhere five stack levels below you in the darkest corner of your application someone has decided to remove that element that you expected to be there.

Pyrsistent is influenced by persistent data structures such as those found in the standard library of Clojure. The data structures...

Read as markdown · JSON record · Source repository · Homepage

AI interpretation — verify before relying

AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

Pyrsistent provides immutable, persistent collections (vectors, maps, sets, records, and more) where all mutations return new copies, leaving originals unchanged and eliminating hidden side effects.

Installation is straightforward with a pure-wheel distribution and no runtime dependencies. The package is aging (last release October 2023, over 1000 days old) but remains actively maintained with a stable repository and 2196 GitHub stars.

MIT license permits unrestricted use, modification, and distribution with minimal restrictions—suitable for both open-source and commercial projects.

Usage

pip install pyrsistent==0.20.0

from pyrsistent import v, m, s

v1 = v(1, 2, 3)
v2 = v1.append(4)
m1 = m(a=1, b=2)
m2 = m1.set('c', 3)
s1 = s(1, 2, 3)
s2 = s1.add(4)

Requires Python 3.8 or later.

Verdict: Pyrsistent is a mature, well-established library for functional-style immutable collections with zero runtime dependencies and permissive licensing. While aging (1000+ days since last release), its stable maintenance status, broad Python version support (3.8–3.12, PyPy), and absence of known vulnerabilities make it a reliable choice for projects requiring persistent data structures.

Needs verification

Whether the 1000-day gap since last release reflects active maintenance or dormancy despite the repository not being archived
Performance characteristics and memory overhead compared to standard Python collections for typical use cases

immutable data structures pythonpersistent collections functionalimmutable vector map setfunctional data structures clojure-likeside-effect-free collectionsimmutable records with type checkinghashable persistent data structures