antidote 0.13.0

Dependency injection.

Antidotes is a dependency injection micro-framework for Python 3.6+. It is built on the idea of ensuring best maintainability of your code while being as easy to use as possible. It also provides the fastest injection with @inject allowing you to use it virtually anywhere and fast full isolation of your tests.

Antidote provides the following features:

• Ease of use

  • Injection anywhere you need through a decorator @inject, be it static methods, functions, etc.. By default, it will only rely on annotated type hints, but it supports a lot more!

  • No **kwargs arguments hiding actual arguments and fully mypy typed, helping you and your IDE.

  • Documented, everything has tested examples.

  • No need for any custom setup, just use your injected function as usual. You just don’t have to specify injected arguments anymore. Allowing you to gradually migrate an existing project.

• Flexibility

  • Most common dependencies out of the box: services, configuration, factories, interface/implementation.

  • All of those are implemented on top of the core implementation. If Antidote doesn’t provide what you need, there’s a good chance you can implement it yourself.

  • scope support

  • async injection

• Maintainability

  • All dependencies can be tracked back to their declaration/implementation easily.

  • Mypy compatibility and usage of type hints as much as possible.

  • Overriding dependencies will raise an error outside of tests.

  • Dependencies can be frozen, which blocks any new declarations.

  • No double injection.

  • Everything is as explicit as possible, @inject does not inject anything implicitly.

  • type checks when a type is explicitly defined with world.get, world.lazy and constants.

  • thread-safe, cycle detection.

• Testability

  • @inject lets you override any injections by passing explicitly the arguments.

  • fully isolate each test with world.test.clone. They will work on the separate objects.

  • Override any dependency locally in a test.

  • When encountering issues you can retrieve the full dependency tree, nicely formatted, with world.debug.

• Performance*

  • fastest @inject with heavily tuned Cython.

  • As much as possible is done at import time.

  • testing utilities are tuned to ensure that even with full isolation it stays fast.

  • benchmarks: comparison, injection, test utilities

*with the compiled version, in Cython. Pre-built wheels for Linux. See further down for more details.

Installation

To install Antidote, simply run this command:

pip install antidote

Documentation

Beginner friendly tutorial, recipes, the reference and a FAQ can be found in the documentation.

Here are some links:

• Why dependency injection ?

• Why use a dependency injection framework ?

• Why choose Antidote ?

• Getting Started

• Changelog

Issues / Feature Requests / Questions

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

Hands-on quick start

Showcase of the most important features of Antidote with short and concise examples. Checkout the Getting started for a full beginner friendly tutorial.

Injection, Service and Constants

How does injection looks like ?

from typing import Annotated
# from typing_extensions import Annotated # Python < 3.9
from antidote import Service, inject, Provide

class Database(Service):
    pass

@inject
def f(db: Provide[Database]):
    pass

f()  # works !

Simple, right ? And you can still use it like a normal function, typically when testing it:

f(Database())

@inject supports a lot of different ways to express which dependency should be used, the most important ones are:

• annotated type hints:

  @inject
  def f(db: Provide[Database]):
      pass

• list:

  @inject([Database])
  def f(db):
      pass

• dictionary:

  @inject({'db': Database})
  def f(db):
      pass

• auto_provide

  # All class type hints are treated as dependencies
  @inject(auto_provide=True)
  def f(db: Database):
      pass

Now let’s get back to our Database. It lacks some configuration !

from antidote import inject, Service, Constants, const

class Config(Constants):
    DB_HOST = const('localhost:5432')

class Database(Service):
    @inject([Config.DB_HOST])  # self is ignored when specifying a list
    def __init__(self, host: str):
        self._host = host

@inject({'db': Database})
def f(db: Database):
    pass

f()  # yeah !

Looks a bit overkill here, but doing so allows you to change later how DB_HOST is actually retrieved. You could load a configuration file for example, it wouldn’t change the rest of your code. And you can easily find where a configuration parameter is used.

You can also retrieve dependencies by hand when testing for example:

from antidote import world

# Retrieve dependencies by hand, in tests typically
world.get(Config.DB_HOST)
world.get[str](Config.DB_HOST)  # with type hint
world.get[Database]()  # omit dependency if it's the type hint itself

If you want to be compatible with Mypy type checking, you just need to do the following:

@inject
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

This might look a bit cumbersome, but in reality you’ll only need to do it in functions you are actually calling yourself in your code. Typically Database.__init__() won’t need it because it’ll always be Antidote injecting the arguments.

Factories and Interface/Implementation

Want more ? Here is an over-engineered example to showcase a lot more features. First we have an ImdbAPI coming from a external library:

# from a library
class ImdbAPI:
    def __init__(self, host: str, port: int, api_key: str):
        pass

You have your own interface to manipulate the movies:

# movie.py
class MovieDB:
    """ Interface """

    def get_best_movies(self):
        pass

Now that’s the entry point of your application:

# main.py
from movie import MovieDB
from current_movie import current_movie_db


@inject([MovieDB @ current_movie_db])
def main(movie_db: MovieDB = None):
    assert movie_db is not None  # for Mypy, to understand that movie_db is optional
    pass

# Or with annotated type hints
@inject
def main(movie_db: Annotated[MovieDB, From(current_movie_db)]):
    pass

main()

Note that you can search for the definition of current_movie_db. So you can simply use “Go to definition” of your IDE which would open:

# current_movie.py
# Code implementing/managing MovieDB
from antidote import factory, inject, Service, implementation
from config import Config

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

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

    def get_best_movies(self):
        pass

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

Or with annotated type hints:

# current_movie.py
# Code implementing/managing MovieDB
from antidote import factory, Service, Get, From
from typing import Annotated
# from typing_extensions import Annotated # Python < 3.9
from config import Config

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

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

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

    def get_best_movies(self):
        pass

The configuration can also be easily tracked down:

# config.py
from antidote import Constants, const

class Config(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):
        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_conf[root][key]

Testing and Debugging

Based on the previous example. You can test your application by simply overriding any of the arguments:

conf = Config()
main(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,
)))

You can also fully isolate your tests from each other while relying on Antidote and override any dependencies within that context:

from antidote import world

# Clone current world to isolate it from the rest
with world.test.clone():
    # Override the configuration
    world.test.override.singleton(Config.IMDB_HOST, 'other host')
    main()

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(main)
# will output:
"""
main
└── Permanent implementation: MovieDB @ current_movie_db
    └──<∅> IMDBMovieDB
        └── ImdbAPI @ imdb_factory
            └── imdb_factory
                ├── Const: Config.IMDB_API_KEY
                │   └── Config
                ├── Const: Config.IMDB_PORT
                │   └── Config
                └── Const: Config.IMDB_HOST
                    └── Config

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 !

Compiled

The compiled implementation is roughly 10x faster than the Python one and strictly follows the same API than the pure Python implementation. Pre-compiled wheels are available only for Linux currently. You can check whether you’re using the compiled version or not with:

from antidote import is_compiled

print(f"Is Antidote compiled ? {is_compiled()}")

You can force the compilation of antidote yourself when installing:

ANTIDOTE_COMPILED=true pip install antidote

On the contrary, you can force the pure Python version with:

pip install --no-binary antidote

Note

The compiled version is not tested against PyPy. The compiled version relies currently on Cython, but it is not part of the public API. Relying on it in your own Cython code is at your risk.

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.