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‎README.rst

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@@ -52,7 +52,7 @@ What is ``Dependency Injector``?
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``Dependency Injector`` is a dependency injection framework for Python.
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It helps you implement the dependency injection principle.
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It helps you in implementing the dependency injection principle.
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What is dependency injection?
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-----------------------------
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.. code-block:: python
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import os
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class ApiClient:
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def __init__(self):
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def __init__(self):
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self.api_client = ApiClient()
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if __name__ == '__main__':
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service = Service()
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After:
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.. code-block:: python
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import os
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class ApiClient:
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def __init__(self, api_key: str, timeout: int):
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def __init__(self, api_client: ApiClient):
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self.api_client = api_client
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Who creates the objects now? Look at the next section.
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if __name__ == '__main__':
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service = Service(ApiClient(os.getenv('API_KEY'), os.getenv('TIMEOUT')))
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Flexibility comes with a price: now you need to assemble your objects like this
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``Service(ApiClient(os.getenv('API_KEY'), os.getenv('TIMEOUT')))``. The assembly code might get
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duplicated and it'll become harder to change the application structure.
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What does Dependency Injector do?
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---------------------------------
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``Dependency Injector`` provides you with the container and the providers that help you build
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your application objects when you apply dependency injection principle:
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``Dependency Injector`` helps you assemble the objects.
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It provides you the container and the providers that help you describe objects assembly. When you
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need an object you get it from the container. The rest of the assembly work is done by the
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framework:
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.. code-block:: python
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from dependency_injector import containers, providers
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from unittest import mock
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from dependency_injector import containers, providers
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class ApiClient:
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def __init__(self, api_key: str, timeout: int):
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self.api_key = api_key
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self.timeout = timeout
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from .example_di import ApiClient, Service
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class Service:
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def __init__(self, api_client: ApiClient):
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self.api_client = api_client
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class Container(containers.DeclarativeContainer):
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class Container(containers.DeclarativeContainer):
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config = providers.Configuration()
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config = providers.Configuration()
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api_client = providers.Singleton(
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ApiClient,
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api_key=config.api_key,
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timeout=config.timeout,
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)
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api_client = providers.Singleton(
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ApiClient,
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api_key=config.api_key,
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timeout=config.timeout,
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)
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service = providers.Factory(
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Service,
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api_client=api_client,
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)
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service = providers.Factory(
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Service,
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api_client=api_client,
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)
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if __name__ == '__main__':
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container = Container()
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container.config.api_key.from_env('API_KEY')
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container.config.timeout.from_env('TIMEOUT')
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service = container.service()
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assert isinstance(service.api_client, ApiClient)
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Retrieving of the ``Service`` instance now is done like this ``container.service()``.
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Also ``Dependency Injector`` provides a bonus in overriding any of the providers with the
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``.override()`` method:
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.. code-block:: python
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from unittest import mock
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if __name__ == '__main__':
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container = Container()
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container.config.from_yaml('config.yml')
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service = container.service()
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assert isinstance(service.api_client, ApiClient)
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with container.api_client.override(mock.Mock()):
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service = container.service()
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assert isinstance(service.api_client, mock.Mock)
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with container.api_client.override(mock.Mock()):
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service = container.service()
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assert isinstance(service.api_client, mock.Mock)
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It helps in a testing. Also you can use it for configuring project for the different environments:
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replace an API client with a stub on the dev or stage.
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`More examples <https://github.com/ets-labs/python-dependency-injector/tree/master/examples>`_
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‎examples/di_demo2/config.yml

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This file was deleted.

‎examples/di_demo2/demo.py

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Original file line numberDiff line numberDiff line change
@@ -1,7 +1,17 @@
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from dependency_injector import containers, providers
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from unittest import mock
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from .example_di import ApiClient, Service
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class ApiClient:
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def __init__(self, api_key: str, timeout: int):
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self.api_key = api_key
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self.timeout = timeout
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class Service:
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def __init__(self, api_client: ApiClient):
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self.api_client = api_client
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class Container(containers.DeclarativeContainer):
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if __name__ == '__main__':
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container = Container()
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container.config.from_yaml('config.yml')
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container.config.api_key.from_env('API_KEY')
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container.config.timeout.from_env('TIMEOUT')
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service = container.service()
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assert isinstance(service.api_client, ApiClient)
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with container.api_client.override(mock.Mock()):
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service = container.service()
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assert isinstance(service.api_client, mock.Mock)

‎examples/di_demo2/example_di.py

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import os
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class ApiClient:
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def __init__(self, api_client: ApiClient):
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self.api_client = api_client
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if __name__ == '__main__':
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service = Service(ApiClient(os.getenv('API_KEY'), os.getenv('TIMEOUT& CA11 #39;)))

‎examples/di_demo2/example_no_di.py

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@@ -12,3 +12,7 @@ class Service:
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def __init__(self):
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self.api_client = ApiClient()
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if __name__ == '__main__':
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service = Service()

‎examples/di_demo2/test.py

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from unittest import mock
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from demo import Container
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if __name__ == '__main__':
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container = Container()
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with container.api_client.override(mock.Mock()):
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service = container.service()
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assert isinstance(service.api_client, mock.Mock)

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