oslash
Functional library for Functors, Applicatives, and Monads in Python 3.12+
Decision gist · record as of 2026-08-14
Yes, if your goal is learning functional programming concepts or teaching them to others. The modern type system, strict Pyright checking, and educational focus make it a solid learning resource. No, if you need production-grade functional programming—use Expression instead. The aging maintenance status is not a blocker for a stable educational library, but verify that tutorials and examples match version 2.0.0.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.12 or later; earlier versions are not supported.
- Low friction: pure Python wheel with no runtime dependencies.
- Maintenance is aging—last release 270 days old—but the repo remains active and the package is marked Production/Stable.
License · maintenance · safety
permissive license (permissive) — MIT license (permissive). You can use, modify, and distribute OSlash freely in commercial or private projects with minimal restrictions.
last release 2025-11-17 (270 days) · last repo commit 2025-11-17 · 756 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 121,905 downloads/mo, #11,969 on PyPI
Alternatives
Verify before relying
pip install oslash
from oslash import Just
result = Just(2).map(lambda x: x + 3)
print(result) # Just 5- Whether the library is actively maintained beyond the aging maintenance status signal—last commit date suggests recent activity but release cadence is unclear.
- Performance characteristics and whether OSlash is suitable for computationally intensive functional workflows beyond educational use.
What it is and what it does
OSlash is a Python library that teaches and demonstrates functional programming by implementing Haskell-style abstractions—Functor, Applicative, Monad, and concrete monads like Maybe, Either, IO, Writer, Reader, and State. It uses Python 3.12's modern type system (PEP 695 syntax) and is fully type-checked with Pyright in strict mode, making it a learning tool rather than a production framework.
The library unifies functional and object-oriented paradigms by wrapping functions in classes and avoiding mutable state; data lives only in function closures. It provides monadic sequencing operators, lifting, composition, and utility functions. The author explicitly recommends Expression for production functional programming; OSlash is designed as a tutorial implementation to understand how these concepts work.
Use it for
- Learning functional programming concepts by studying and experimenting with Haskell-style abstractions in Python.
- Understanding how Maybe and Either monads handle optional values and error cases without exceptions.
- Exploring IO monads and Reader/Writer patterns for managing side effects and logging in a functional style.
- Teaching functional programming principles to Python developers using a type-safe, well-documented codebase.
- Prototyping functional algorithms and compositions before porting to a production functional library.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if your goal is learning functional programming concepts or teaching them to others.
The modern type system, strict Pyright checking, and educational focus make it a solid learning resource. No, if you need production-grade functional programming—use Expression instead. The aging maintenance status is not a blocker for a stable educational library, but verify that tutorials and examples match version 2.0.0.
Install
oslash on PyPI
Before you install
Low friction: pure Python wheel with no runtime dependencies. Maintenance is aging—last release 270 days old—but the repo remains active and the package is marked Production/Stable.
Requires Python 3.12 or later; earlier versions are not supported.
License in practice
MIT license (permissive). You can use, modify, and distribute OSlash freely in commercial or private projects with minimal restrictions.
Quickstart
pip install oslash
from oslash import Just
result = Just(2).map(lambda x: x + 3)
print(result) # Just 5Verify before relying
- Whether the library is actively maintained beyond the aging maintenance status signal—last commit date suggests recent activity but release cadence is unclear.
- Performance characteristics and whether OSlash is suitable for computationally intensive functional workflows beyond educational use.
Package facts
| License | permissive license permissive |
| Python support | Supports the current Python release >=3.12 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Aging 270 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 121,905 / month, #11,969 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableEnvironment :: Other EnvironmentIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Topic :: Software Development :: Libraries :: Python ModulesTyping :: Typed |
Evidence: oslash-2.0.0-py3-none-any.whl
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