awesome-functional-python

Awesome Functional Python

A curated list of awesome things related to functional programming in Python.

• Official documentation
• Books
• Talks
• Other resources
• Libraries
• Languages

Official documentation

• Functional Programming HOWTO - "In this document, we’ll take a tour of Python’s features suitable for implementing programs in a functional style".

Books

Free books / ebooks

• Functional Programming in Python - Book by David Mertz (O'Reilly).

Non-free books

• Functional Python Programming - Book by Steve Lott (Packtpub, 2015).

Talks

Introductory

• Functional Programming with Python (slides) - Alexey Kachayev, UA PYCon 2012.
• Purely Functional Programming in Python: Pure Fun (slides) - Christopher Armstrong, PyTenessee 2015.
• Side Effects are a Public API (video) - Christopher Armstrong, Strangeloop 2015
• Functional Programming with Python (video) - Mike Müller, PyCon US 2013.
• Using Functional Programming for efficient Data Processing and Analysis (video) - Reuben Cummings, PyCon US 2017.
• Immutable Programming Writing Functional Python (slides, video), Calen Pennington, PyCon 2017.
• Functional Programming inside OOP? It’s possible with Python (Slides) - Carlos Villavicencio, EuroPython 2021.
• A Hitchhiker’s Guide to functools (Slides) - Scott Irwin, EuroPython 2021.
• Writing Functional Code in Python (Video) - Vic Kumar, PyCon 2022

Advanced or specialized

• Functionalish programming in Python with effect (video), Robert Collins, NZ PyCon 2015.
• Monadic Parsing in Python (slides), Alexey Kachayev, KyivPy 2014.
• Immutability and Python - Introducing Pyrsistent (slides), Tobias Gustafsson, 2014.
• Understanding Transducers (slides, video), Austin Bingham, PyCon Belarus 2015.

Data science oriented

• Functional Performance with Core Data Structures (video), Matthew Rocklin, PyData SV 2014.
• Old School - Functional Data Analysis (video), Matthew Rocklin, PyData NYC 2013.
• Learning Data Science Using Functional Python (video, slides), Joel Grus, PyData Seattle 2015.

Other resources

Video lectures (not free)

• Functional Programming with Python - by Christopher Armstrong, O'Reilly.
• Functional Programming in 7 days - by Mohammed Kashif, Udemy.
• Functional Programming in Python - by Dan Bader, Real Python.

Blog posts

• Origins of Python's "Functional" Features, Guido Van Rossum, 2009.
• A practical introduction to functional programming (with examples in Python), by Mary Rose Cook (year unknown).
• Immutable data structures in Python, Robert Rees, 2014.
• Understanding Transducers through Python, by Robert Smallshire. "In this 8 parts series we take an in-depth look at transducers. Transducers – a portmanteau of ‘transform reducers’ – are a new functional programming concept introduced into the Clojure programming language."
• Thinking Functionally with Python and Django at eShares Inc., Kyle Hanson, 2017.
• Simple dependent types in Python - Nikita Sobolev, 2019.
• Python exceptions considered an anti-pattern, Nikita Sobolev, 2019.
• Enforcing Single Responsibility Principle in Python - Nikita Sobolev, 2019.
• Typed functional Dependency Injection in Python - Nikita Sobolev, 2020.
• 4 Part Series on Functional Programming Techniques and Design In Python M. Kocher, 2019.
• Typeclasses in Python - N. Sobolev, 2021
• Functools — The Power of Higher-Order Functions in Python - M. Heinz, 2021
• Tail Recursion Elimination - Guido van Rossum, 2009
• Final Words on Tail Calls - Guido van Rossum, 2009
• The fate of reduce() in Python 3000 - Guido van Rossum, 2005
• Best Practices for Using Functional Programming in Python - Kite Blog, 2018.
• (Dead initiative) Why we need a Python functional programming initiative: a manifesto - Leftfile 2023

Scientific papers

• Practical Functional Reactive Programming (PDF), John Peterson, Ken Roe, and Alan Cleary, 2014.

Presentation slides

• Python Generators, Samuel Lampa, From talk at PySthlm meetup, Oct 2013

Libraries

General

• toolz ★4619 - "A functional standard library for Python".
• more-itertools ★3639 - "More routines for operating on iterables, beyond itertools".
• fn.py ★3348 - "Functional programming in Python: implementation of missing features to enjoy FP" (unmaintained since 2014). Maintained fork.
• funcy ★3333 - "A fancy and practical functional tools".
• PyFunctional ★2380 - "Python library for functional programming with collections in a data pipeline style".
• Pipe ★1898 - "A Python library to use infix notation in Python".
• Pydash ★1291 - "The kitchen sink of Python utility libraries for doing "stuff" in a functional way. Based on the Lo-Dash Javascript library".
• hask ★858 - "Haskell language features and standard libraries in pure Python".
• OSlash ★709 - "Functors, Applicatives, And Monads in Python".
• Expression ★454 - "Pragmatic functional programming for Python inspired by F#". Successor of OSlash.
• Effect ★369 - "Effect isolation in Python, to facilitate more purely functional code".
• Underscore.py ★291 - "A Python port of excellent javascript library underscore.js".
• fnc ★247 - "Functional programming in Python with generators and other utilities".
• Flupy ★192 - Implements a fluent interface for operating on python iterables.
• PyMonad ★189 - "a small library implementing monads and related data abstractions -- functors, applicative functors, and monoids -- for use in implementing functional style programs".
• pfun ★149 - "Pure functional programming in python".
• Phi ★132 - "A library that intends to remove as much of the pain as possible from your functional programming experience in Python."
• pyramda ★127 - "Python package supporting heavy functional programming through currying. Translation of the Ramda library from javascript to python".
• unpythonic ★87 - "Supercharge your Python with parts of Lisp and Haskell."
• ziopy ★75 - "ZIO for Python (with ZIO = A type-safe, composable library for async and concurrent programming in Scala)"
• pyMonet ★34 - "High abstract python library for functional programming. Contains algebraic data structures known from Haskell or Scala".
• Compose ★32 - The classic compose, with all the Pythonic features.
• pyeffects ★30 - "Handle side-effects in Python like a boss. Implements functional types for Either, Option, Try, and Future."
• Iter ★10 - map, filter etc. as methods on a sequence.

Return types

• returns ★3421 - "Make your functions return something meaningful, typed, and safe!"
• result ★1458 - A simple Rust like Result type for Python 3. Fully type annotated.
• Option ★84 - Rust-like Option and Result types in Python.
• Meiga ★76 - A simple, typed and monad-based Result type for Python.
• Safetywrap ★43 - Fully typesafe, Rust-like Result and Option types for Python.

Immutable / persistent data structures

• Pyrsistent ★2005 - "Persistent/Immutable/Functional data structures for Python".
• Immutables ★1116 - "An immutable mapping type for Python."

Dead projects:

• Discodb ★98 - "An efficient, immutable, persistent mapping object".
• Funktown ★74 - "Immutable Data Structures for Python".
• Amino ★35 - "functional data structures and type classes".
• Pysistence - "Pysistence is a project that seeks to make functional programming in python easier".

Pattern matching

Note: Pattern matching is now a standard feature in Python 3.10.

• pampy ★3511 - "Pampy: The Pattern Matching for Python you always dreamed of."
• python-pattern-matching ★161 - "Python pattern matching like functional languages."
• patmat ★30 - "Functional-style recursive pattern matching in Python. Crazy stuff."
• apm ★107 - "Pattern Matching for Python 3.8+ in a simple, yet powerful, extensible manner."

Tranducers

(Both projects are dead).

• Tranducers-Python ★202 - "Transducers are composable algorithmic transformations".
• Transducers ★55 - "This is a port of the transducer concept from Clojure to Python, with an emphasis on providing as Pythonic as interpretation of transducers as possible, rather than reproducing Clojurisms more literally".

Support for reactive style

• RxPy ★4727 - "Reactive Extensions for Python".
• broqer ★74 - "Library to operate with continuous streams of data in a reactive style"
• sodium-python ★3 - "Python implementation of Sodium - Functional Reactive Programming (FRP) Library"

Lenses and declarative data manipulations

• Glom ★1868 - "Python's nested data operator (and CLI), for all your declarative restructuring needs.".
• python-lenses ★304 - "A python lens library for manipulating deeply nested immutable structures".

Other / specialized

• deal ★719 - "Design by contract for Python with many validators support."
• classes ★651 - "Smart, pythonic, ad-hoc, typed polymorphism for Python."
• chainable ★192 - "Method chaining built on generators".
• ADT ★172 - Algebraic data types for Python
• sumtypes ★42 - "Sum Types, aka Tagged Unions, for Python".
• python-mini-lambda ★13 - "Simple Lambda functions without lambda x: and with string conversion capability"
• Orinoco ★11 - "Functional composable pipelines allowing clean separation of the business logic and its implementation"
• slist ★11 - "A drop-in replacement for the python mutable list. But with much more methods for typesafe method chaining."
• py-frm ★1 - "Proof-of-concept Functional-Relational Mapping (FRM) for Python"

Languages

Functional programming languages that are not Python but are related to the Python ecosystem:

Active languages

• Hy ★4822 -