python-di

Fully automatic dependency injection for python 3.7, 3.8, 3.9, pypy3 using (not only) argument annotations / type hints.

Corresponds to clean architecture patterns and ideal for business applications created in DDD / Hexagonal architecture flavour. No external dependencies - uses only standard libraries.

Key features:

• automatic type matching based on type hints / type annotations - no manual configuration is needed, it just works out of the box
• configurable object aggregation injection - DI can join SomeClass objects and inject into argument annotated as Collection[SomeClass]
• not harm existing codebase - no decorators, no extra metadata are needed in existing codebase to make app construction possible
• no singletons or global DI process state - app or any app components can be instantiated independently as many times as needed
• transparency of DI process - static dependency graph and injection plan is built, informative exceptions on error cases (like cyclic dependency or missing elements)

Help

Coming soon...

An Example

Application domain located in mod_simple.py:

from typing import List


class Repo:
    def read(self) -> List[str]:
        raise NotImplementedError


class DomainAction:
    def __init__(self, repo: Repo):
        self.repo = repo

    def present(self) -> str:
        joined = ", ".join(self.repo.read())
        return f"Data found: {joined}"

Application concretes located in mod_simple_impl.py:

from typing import List

from mod_simple import Repo


class MockupRepo(Repo):
    def read(self) -> List[str]:
        return ["di", "test"]

Automatic application construction:

from di.declarative import DeclarativeApp, DeclarativeModule, scan_factories
import mod_simple, mod_simple_impl


def main():
    # create app definition
    app_def = DeclarativeApp(
        DeclarativeModule(
            # automatically add factories from `mod_simple` and `mod_simple_impl`
            scan_factories(mod_simple, mod_simple_impl),
        )
    )

    # build app
    instance = app_def.build_instance()

    # get initialized `DomainAction` object
    action, = instance.values_by_type(mod_simple.DomainAction)

    # check app works
    assert action.present() == "Data found: di, test"

More examples

More working examples are available in tests/di/declarative/. Please see tests/di/declarative/test_build.py for reference.