I created fastapi-injectable to solve a common pain point in FastAPI: using Depends() outside of route handlers. This has been a long-standing issue in the FastAPI community with a discussion post around it.

Install with: pip install fastapi-injectable

The package lets you use FastAPI's dependency injection in:

- CLI tools

- Background workers

- Test fixtures

- Any non-HTTP context

Basic example:

    from typing import Annotated

    from fastapi import Depends
    from fastapi_injectable import injectable

    class Database:
        def query(self) -> str:
            return "data"

    def get_db() -> Database:
        return Database()

    @injectable
    def process_data(db: Annotated[Database, Depends(get_db)]) -> str:
        return db.query()

    # Use it anywhere!
    result = process_data()
    print(result) # Output: 'data'

The common suggestion for handling dependencies outside FastAPI routes is to use separate DI frameworks like dependency-injector. However, this means:

1. Managing two different DI systems in your codebase

2. Learning another framework's patterns

3. Potentially duplicating dependency logic

Currently, there's no package that extends FastAPI's native Depends() beyond routes.

fastapi-injectable solves this by providing a clean API that lets you use FastAPI's dependency injection anywhere.

Links:

GitHub: https://github.com/your-username/fastapi-injectable

Docs: https://fastapi-injectable.readthedocs.io

PyPI: https://pypi.org/project/fastapi-injectable

I'd love to hear your feedback and contributions to make this package better! Feel free to open issues or PRs if you have ideas for improvements.