FastAPI Injectable

1.4.7 verified Sat May 09 auth: no python

Use FastAPI's Depends() anywhere — in CLI tools, Celery tasks, background workers, and more. No refactoring needed. Current version: 1.4.7. Python >=3.10. Active development.

pip install fastapi-injectable

Common errors

error RuntimeError: You cannot use AsyncToSync in the same thread as an async event loop ↓

cause Calling get_injected_obj() inside an already running async context.

fix

Use async_get_injected_obj() instead: from fastapi_injectable import async_get_injected_obj; result = await async_get_injected_obj(func)

error ImportError: cannot import name 'get_injected_obj' from 'fastapi_injectable.util' ↓

cause Using the internal module path instead of the public API.

fix

Use: from fastapi_injectable import get_injected_obj

error TypeError: 'Depends' object is not callable ↓

cause Passing Depends() as a parameter without annotating with Annotated.

fix

Use Annotated[type, Depends(dependency)] syntax, e.g., DepDB = Annotated[str, Depends(get_db)]

error AttributeError: 'NoneType' object has no attribute 'dependency_overrides' ↓

cause Passing a FastAPI app that is None to get_injected_obj.

fix

Ensure the app parameter is not None when using overrides, or omit it.

Warnings

gotcha get_injected_obj() can fail with 'event loop already running' if called from an async context like an async callback or Kafka consumer. Use async_get_injected_obj() instead when already inside a running event loop. ↓

fix Replace get_injected_obj with async_get_injected_obj when in an async context.

deprecated Direct import from fastapi_injectable.util (e.g., from fastapi_injectable.util import get_injected_obj) is considered internal and may change without notice. ↓

fix Use from fastapi_injectable import get_injected_obj.

breaking In v1.4.5, the internal async exit stack management changed. If you manually managed exit stacks, your code may break. ↓

fix Let fastapi-injectable handle stack management; avoid overriding internal AsyncExitStack.

gotcha Dependency overrides set via app.dependency_overrides are NOT automatically respected unless you use get_injected_obj with the updated override mechanism (v1.4.0+). ↓

fix Use the override parameter of get_injected_obj or ensure app.dependency_overrides is applied before calling.

Imports

get_injected_obj

wrong

from fastapi_injectable.util import get_injected_obj

correct

from fastapi_injectable import get_injected_obj

The public API is at package level, not under util.

async_get_injected_obj

wrong

from fastapi_injectable.util import async_get_injected_obj

correct

from fastapi_injectable import async_get_injected_obj

Use the top-level import for async variant.

Injectable

wrong

from fastapi_injectable.decorator import Injectable

correct

from fastapi_injectable import Injectable

Injectable class is exposed at package level.

Quickstart

Inject FastAPI-style dependencies anywhere, even outside an async context.

from fastapi import Depends
from fastapi_injectable import get_injected_obj
from typing import Annotated

async def get_db() -> str:
    return "db_session"

DepDB = Annotated[str, Depends(get_db)]

# Use in a non-FastAPI context (e.g., Celery task)
def worker(dep: DepDB) -> None:
    print(dep)

# Inject dependencies outside FastAPI
obj = get_injected_obj(worker)
print(obj)