antidote 0.12.0

Installation

To install Antidote, simply run this command:

pip install antidote

Documentation

Beginner friendly tutorial, recipes and the reference can be found at https://antidote.readthedocs.io/en/stable.

Hands-on quick start

Short and concise example of some of the most important features of Antidote.

How does injection looks like ? Here is a simple example:

from antidote import inject, Service, Constants, const, world, Provide, Get
from typing import Annotated
# from typing_extensions import Annotated # Python < 3.9

class Conf(Constants):
    DB_HOST = const[str]('localhost:5432')
    DB_HOST_WITHOUT_TYPE_HINT = const('localhost:5432')

# Declared as a Service
class Database(Service):
    # All methods are decorated with @inject by default
    def __init__(self, host: Annotated[str, Get(Conf.DB_HOST)]):
        self._host = host

@inject  # Uses only annotated type hints by default
def f(db: Provide[Database] = None):
    # Used to tell Mypy that `db` is optional but must be either injected or given.
    assert db is not None
    pass

f()  # yeah !
f(Database('localhost:5432'))  # override injection

# You can also retrieve dependencies by hand
world.get(Conf.DB_HOST)
world.get[str](Conf.DB_HOST)  # with type hint
# if the dependency is the type itself, you may omit it:
world.get[Database]()

Or without annotated type hints (PEP-593):

class Database(Service):
    @inject({'host': Conf.DB_HOST})
    def __init__(self, host: str):
        self._host = host

@inject([Database])
def f(db: Database = None):
    assert db is not None
    pass

# auto_provide => Class type hints are treated as dependencies.
@inject(auto_provide=True)
def f(db: Database = None):
    assert db is not None
    pass

Want more ? Here is an over-engineered example to showcase a lot more features:

# Some library.py
class ImdbAPI:
    def __init__(self, host: str, port: int, api_key: str):
        pass

# The interface exposed in your code
class MovieDB:
    def get_best_movies():
        pass

# Code using MovieDB
@inject
def f(movie_db: Annotated[MovieDB, From(current_movie_db)] = None):
    assert movie_db is not None  # for Mypy
    pass

f()

Now searching for the definition of current_movie_db would lead you to:

# Code implementing/managing MovieDB
from antidote import (Constants, factory, inject, world, const, Service,
                      implementation, Get, From)
from typing import Annotated
# from typing_extensions import Annotated # Python < 3.9

class Conf(Constants):
    # with str/int/float, the type hint is enforced. Can be removed or extend to
    # support Enums.
    IMDB_HOST = const[str]('imdb.host')
    IMDB_PORT = const[int]('imdb.port')
    IMDB_API_KEY = const('imdb.api_key')

    def __init__(self):
        """
        Load configuration from somewhere. You can change how you configure your
        application later, it won't impact the whole application.
        """
        self._raw_conf = {
            'imdb': {
                'host': 'dummy_host',
                'api_key': 'dummy_api_key',
                'port': '80'
            }
        }

    def provide_const(self, name: str, arg: str):
        root, key = arg.split('.')
        return self._raw_const[root][key]

# Provides ImdbAPI, as defined by the return type annotation.
@factory
def imdb_factory(host: Annotated[str, Get(Conf.IMDB_HOST)],
                 port: Annotated[int, Get(Conf.IMDB_PORT)],
                 api_key: Annotated[str, Get(Conf.IMDB_API_KEY)]
                 ) -> ImdbAPI:
    # Here host = Conf().get('imdb.host')
    return ImdbAPI(host=host, port=port, api_key=api_key)

class IMDBMovieDB(MovieDB, Service):
    __antidote__ = Service.Conf(singleton=False)  # New instance each time

    def __init__(self, imdb_api: Annotated[ImdbAPI, From(imdb_factory)]):
        self._imdb_api = imdb_api

    def get_best_movies():
        pass

@implementation(MovieDB)
def current_movie_db():
    return IMDBMovieDB  # dependency to be provided for MovieDB

Or without annotated type hints:

@factory
@inject([Conf.IMDB_HOST, Conf.IMDB_PORT, Conf.IMDB_API_KEY])
def imdb_factory(host: str, port: int, api_key: str) -> ImdbAPI:
    return ImdbAPI(host, port, api_key)

class IMDBMovieDB(MovieDB, Service):
    __antidote__ = Service.Conf(singleton=False)

    @inject({'imdb_api': ImdbAPI @ imdb_factory})
    def __init__(self, imdb_api: ImdbAPI):
        self._imdb_api = imdb_api

@inject([MovieDB @ current_movie_db])
def f(movie_db: MovieDB = None):
    assert movie_db is not None
    pass

We’ve seen that you can override any parameter:

conf = Conf()
f(IMDBMovieDB(imdb_factory(
    # constants can be retrieved directly on an instance
    host=conf.IMDB_HOST,
    port=conf.IMDB_PORT,
    api_key=conf.IMDB_API_KEY,
)))

But if you only to change one part in a complex dependency graph, you can override them locally with:

# Override locally some dependencies:
with world.test.clone(keep_singletons=True):
    world.test.override.singleton(Conf.IMDB_HOST, 'other host')
    f()

If you ever need to debug your dependency injections, Antidote also provides a tool to have a quick summary of what is actually going on:

world.debug(f)
# will output:
"""
f
└── Permanent implementation: MovieDB @ current_movie_db
    └──<∅> IMDBMovieDB
        └── ImdbAPI @ imdb_factory
            └── imdb_factory
                ├── Const: Conf.IMDB_API_KEY
                │   └── Conf
                │       └── Singleton: 'conf_path' -> '/etc/app.conf'
                ├── Const: Conf.IMDB_PORT
                │   └── Conf
                │       └── Singleton: 'conf_path' -> '/etc/app.conf'
                └── Const: Conf.IMDB_HOST
                    └── Conf
                        └── Singleton: 'conf_path' -> '/etc/app.conf'

Singletons have no scope markers.
<∅> = no scope (new instance each time)
<name> = custom scope
"""

Hooked ? Check out the documentation ! There are still features not presented here !

Comparison

Disclaimer: This comparison is mostly based on the documentation of the most popular libraries I know of, not less not more.

Why choose Antidote ?

• Everything is explicit: Some libraries using an @inject-like decorator, such as injector, lagom or python_inject will instantiate any missing arguments. Antidote will only inject dependencies that you have defined as such and only when told so. Making it easier to understand what is injected or not at first glance.

• Flexibility: With the exception of dependency_injector, most libraries will only support services (class), simple factories and singletons. Antidote also provides configuration, interfaces, stateful factories, lazy methods/functions, scopes, async injection.

• Maintainability: Again with the exception of dependency_injector, dependency injection libraries can make it difficult to understand how/where a dependency is created. Typically when declaring a factory for a service (class), you won’t have any way of finding easily the function when using the service. Antidote syntax always ensures that you can. Antidote primary goal is helping you create maintainable code.

• Performance: Antidote’s @inject is heavily tuned for performance in the compiled version (Cython). No other library goes as far. Now whether it’s really useful for a dependency injection library is debatable. But this allows you to use @inject virtually anywhere without any impact. (See benchmarks on the top)

The main difference with dependency_injector is the philosophy of the library. With dependency_injector declaration of dependencies to the container and their implementation are in two separate files:

# my_service.py
# Dependency Injector
class MyService:
    pass

# services.py
# Dependency Injector
from dependency_injector import containers, providers

class Container(containers.DeclarativeContainer):
    my_service = providers.Singleton(MyService)

This implies that you have one more file to maintain. And with a lot of dependencies you start managing either one big container or multiple ones.

However this one big advantage compared to most other dependency injection libraries: it’s easy to understand how dependencies are wired together, making it a lot more maintainable than most libraries. It is especially visible when declaring factories. With dependency_injector you would do something like that:

# services.py
# Dependency Injector
class Container(containers.DeclarativeContainer):
    my_service = providers.Factory(my_factory)

While most other libraries you have no easy way to know how MyService is created by the dependency injection framework:

# services.py
# Injector
@provider
def my_factory() -> MyService:
    pass

@inject
def f(s: MyService):
    pass

# Lagom
container[MyService] = my_factory

@magic_bind_to_container(container)
def f(s: MyService):
    pass

# Python Inject
def config(binder):
    binder.bind(MyService, my_factory)

inject.configure(config)

@inject.autoparams()
def f(s: MyService):
    pass

But with Antidote you can always track back to the definition of a dependency:

from antidote import factory, inject, From

@factory
def my_factory() -> MyService:
    pass

@inject(dict(my_service=MyService @ my_factory))
def f(my_service: MyService):
    pass

# Or with annotated type hints
@inject
def f(my_service: Annotated[MyService, From(my_factory)]):
    pass

IMHO, this makes Antidote on of the, if not the, most maintainable dependency injection library. There is no container to manage and you can always understand the wiring easily.

Cython

The cython implementation is roughly 10x faster than the Python one and strictly follows the same API than the pure Python implementation. This implies that you cannot depend on it in your own Cython code if any. It may be moved to another language.

If you encounter any inconsistencies, please open an issue ! You can avoid the Cython version from PyPI with the following:

pip install --no-binary antidote

Beware that PyPy is only tested with the pure Python version, not the Cython one.

Issues / Feature Requests / Questions

Feel free to open an issue on Github for questions, requests or issues ! ;)

How to Contribute

1. Check for open issues or open a fresh issue to start a discussion around a feature or a bug.

2. Fork the repo on GitHub. Run the tests to confirm they all pass on your machine. If you cannot find why it fails, open an issue.

3. Start making your changes to the master branch.

4. Writes tests which shows that your code is working as intended. (This also means 100% coverage.)

5. Send a pull request.

Be sure to merge the latest from “upstream” before making a pull request!

If you have any issue during development or just want some feedback, don’t hesitate to open a pull request and ask for help !

Pull requests will not be accepted if:

• classes and non trivial functions have not docstrings documenting their behavior.

• tests do not cover all of code changes (100% coverage) in the pure python.

If you face issues with the Cython part of Antidote just send the pull request, I can adapt the Cython part myself.