runtime-generics 1.1.0

Reuse type arguments explicitly passed at runtime to a generic class before instantiating.

runtime_generics

Highly into type-safe Python code?

runtime_generics is a niche Python library that allows you to reuse type arguments explicitly passed at runtime to generic classes before instantiation. The library does two things:

• makes it possible to retrieve the type argument passed to the generic class at runtime before the class was instantiated;
• given a parametrized generic class (generic alias), it makes every class method use generic alias cls instead of the origin class.

Simple example

3.12+ (PEP 695 syntax):

from runtime_generics import runtime_generic, select

@runtime_generic
class MyGeneric[T]:
    type_argument: type[T]

    def __init__(self) -> None:
        self.type_argument = select[T](self)

    @classmethod
    def whoami(cls):
        print(f"I am {cls}")

my_generic = MyGeneric[int]()
assert my_generic.type_argument is int
my_generic.whoami()  # I am MyGeneric[int]

3.8+:

from __future__ import annotations

from typing import Generic, TypeVar
from runtime_generics import runtime_generic, select

T = TypeVar("T")

@runtime_generic
class MyGeneric(Generic[T]):
    type_argument: type[T]

    def __init__(self) -> None:
        self.type_argument = select[T](self)

    @classmethod
    def whoami(cls):
        print(f"I am {cls}")

my_generic = MyGeneric[int]()
assert my_generic.type_argument is int
my_generic.whoami()  # I am MyGeneric[int]

Installation

If you want to…

…use this tool in your project 💻

You might simply install it with pip:

pip install runtime-generics

If you use Poetry, then run:

poetry add runtime-generics

…contribute to runtime_generics 🚀

Happy to accept contributions!

[!Note] If you use Windows, it is highly recommended to complete the installation in the way presented below through WSL2.

First, install Poetry.
Poetry is an amazing tool for managing dependencies & virtual environments, building packages and publishing them.

pipx install poetry

_{If you encounter any problems, refer to the official documentation for the most up-to-date installation instructions.}

Be sure to have Python 3.8 installed—if you use pyenv, simply run:

pyenv install 3.8

Then, run:

git clone https://github.com/bswck/runtime_generics path/to/runtime_generics
cd path/to/runtime_generics
poetry env use $(cat .python-version)
poetry install
poetry shell
pre-commit install --hook-type pre-commit --hook-type pre-push

Legal info

© Copyright by Bartosz Sławecki (@bswck).
This software is licensed under the MIT License.