https://github.com/orsinium-labs/eff

Python library to work with algebraic effects
https://github.com/orsinium-labs/eff

algebraic-effects dependency-injection effects python side-effects

Last synced: 3 days ago
JSON representation

Python library to work with algebraic effects

• Host: GitHub
• URL: https://github.com/orsinium-labs/eff
• Owner: orsinium-labs
• License: mit
• Created: 2020-11-16T11:38:45.000Z (almost 4 years ago)
• Default Branch: master
• Last Pushed: 2020-11-17T15:18:29.000Z (almost 4 years ago)
• Last Synced: 2024-10-01T09:23:43.007Z (about 1 month ago)
• Topics: algebraic-effects, dependency-injection, effects, python, side-effects
• Language: Python
• Homepage:
• Size: 4.88 KB
• Stars: 66
• Watchers: 5
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# Eff

Eff is a Python library to work with algebraic effects.

Algbraic effects are all side-effects of a piece of code, like reading a user input, writing a text on the screen, doing network requests, reading a file etc. Eff allows to easily handle such effects making the code cleaner and testing easier.

Features:

+ **Easy to understand**. You don't need to read long scientific papers to understand how to use the library and what it does.

+ **Easy to integrate**. If you decided to add a logger into a function, changes will be minimal, no need to pass the logger down through the whole call stack.

+ **Fast**. The classic approach for handling algebraic effects is using coroutines or exceptions. This library uses global shared state instead which doesn't require to unwrap the whole call stack at runtime.

+ **Type-safe**. Effect handlers container is just a class. Annotate effect handlers type to make their usage type-safe.

## Installation

```bash

python3 -m pip install --user eff

```

## Usage

```python

from io import StringIO

from typing import Callable

import eff

class Eff(eff.ects):

    show: Callable

# Use global effects manager in a function.

def greet(username: str) -> None:

    Eff.show(f'Hello, {username}!')

# Provide actual side-effects handlers

# for the project prod entry point.

def main() -> None:

    with Eff(show=print):

        greet('World')

# Mock side-effects in tests.

def test_greet() -> None:

    stream = StringIO()

    with Eff(show=stream.write):

        greet('World')

    stream.seek(0)

    assert stream.read() == 'Hello, World!'

if __name__ == '__main__':

    main()

```

## Further reading

You don't have to read it but it's a good reading for better understanding of the motivation behind the library.

+ [Why PLs Should Have Effect Handlers](https://robotlolita.me/diary/2018/10/why-pls-need-effects/)

+ [Algebraic Effects for the Rest of Us](https://overreacted.io/algebraic-effects-for-the-rest-of-us/)

+ [What does algebraic effects mean in FP?](https://stackoverflow.com/a/57280373)

+ [Eff programming language](https://www.eff-lang.org/)