Type Unions

typeunions is a library providing algebraic data types in Python, with a clean and intuitive syntax that use all the strength of match and dataclass in python 3.10

Install

pip install typeunions

Usage

@typeunion
class Message
    Quit: ()
    Move: { 'x': int, 'y': int }
    Write: (str)
    ChangeColor: (int, int, int)

Each types (Quit, Move, Write, ChangeColor) is a python dataclass. Hence you can use the match case pattern:

message = Message.ChangeColor(255, 128, 0)

match message:
    case Quit: print("quit")
    case Move(x, y): print(f"move {x} {y}")
    case Write(s): print(s)
    case ChangeColor(r, g, b): print(f"{r}{g}{b}")
    case _: print("error")

Here is an exemple of the same code with rust enum

enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

match message {
    Quit => println!("quit")
    Move(x, y) => println!("move {} {}", x, y)
    Write(s) => println!(s)
    ChangeColor(r, g, b) => println!(f"{}{}{}", r, g, b)
}