.. _aiohttp-tutorial: Aiohttp tutorial ================ .. meta:: :keywords: Python,Aiohttp,Tutorial,Education,Web,API,REST API,Example,DI,Dependency injection, IoC,Inversion of control,Refactoring,Tests,Unit tests,Pytest,py.test,Bootstrap, HTML,CSS :description: This tutorial shows how to build an aiohttp application following the dependency injection principle. You will create the REST API application, connect to the Giphy API, cover it with the unit test and make some refactoring. This tutorial shows how to build an ``aiohttp`` REST API application following the dependency injection principle. Start from the scratch or jump to the section: .. contents:: :local: :backlinks: none You can find complete project on the `Github `_. What are we going to build? --------------------------- .. image:: https://media.giphy.com/media/apvx5lPCPsjN6/source.gif We will build a REST API application that searches for funny GIFs on the `Giphy `_. Let's call it Giphy Navigator. How does Giphy Navigator work? - Client sends a request specifying the search query and the number of results. - Giphy Navigator returns a response in json format. - The response contains: - the search query - the limit number - the list of gif urls Example response: .. code-block:: json { "query": "Dependency Injector", "limit": 10, "gifs": [ { "url": "https://giphy.com/gifs/boxes-dependent-swbf2-6Eo7KzABxgJMY" }, { "url": "https://giphy.com/gifs/depends-J56qCcOhk6hKE" }, { "url": "https://giphy.com/gifs/web-series-ccstudios-bro-dependent-1lhU8KAVwmVVu" }, { "url": "https://giphy.com/gifs/TheBoysTV-friends-friend-weneedeachother-XxR9qcIwcf5Jq404Sx" }, { "url": "https://giphy.com/gifs/netflix-a-series-of-unfortunate-events-asoue-9rgeQXbwoK53pcxn7f" }, { "url": "https://giphy.com/gifs/black-and-white-sad-skins-Hs4YzLs2zJuLu" }, { "url": "https://giphy.com/gifs/always-there-for-you-i-am-here-PlayjhCco9jHBYrd9w" }, { "url": "https://giphy.com/gifs/stream-famous-dollar-YT2dvOByEwXCdoYiA1" }, { "url": "https://giphy.com/gifs/i-love-you-there-for-am-1BhGzgpZXYWwWMAGB1" }, { "url": "https://giphy.com/gifs/life-like-twerk-9hlnWxjHqmH28" } ] } The task is naive and that's exactly what we need for the tutorial. Prepare the environment ----------------------- Let's create the environment for the project. First we need to create a project folder: .. code-block:: bash mkdir giphynav-aiohttp-tutorial cd giphynav-aiohttp-tutorial Now let's create and activate virtual environment: .. code-block:: bash python3 -m venv venv . venv/bin/activate Environment is ready and now we're going to create the layout of the project. Project layout -------------- Create next structure in the current directory. All files should be empty. That's ok for now. Initial project layout:: ./ ├── giphynavigator/ │ ├── __init__.py │ ├── application.py │ ├── containers.py │ └── handlers.py ├── venv/ └── requirements.txt Install the requirements ------------------------ Now it's time to install the project requirements. We will use next packages: - ``dependency-injector`` - the dependency injection framework - ``aiohttp`` - the web framework - ``aiohttp-devtools`` - the helper library that will provide a development server with live reloading - ``pyyaml`` - the YAML files parsing library, used for the reading of the configuration files - ``pytest-aiohttp`` - the helper library for the testing of the ``aiohttp`` application - ``pytest-cov`` - the helper library for measuring the test coverage Put next lines into the ``requirements.txt`` file: .. code-block:: bash dependency-injector aiohttp aiohttp-devtools pyyaml pytest-aiohttp pytest-cov and run next in the terminal: .. code-block:: bash pip install -r requirements.txt Let's also install the ``httpie``. It is a user-friendly command-line HTTP client for the API era. We will use it for the manual testing. Run the command in the terminal: .. code-block:: bash pip install httpie The requirements are setup. Now we will build a minimal application. Minimal application ------------------- In this section we will build a minimal application. It will have an endpoint that will answer our requests in json format. There will be no payload for now. Edit ``handlers.py``: .. code-block:: python """Handlers module.""" from aiohttp import web async def index(request: web.Request) -> web.Response: query = request.query.get("query", "Dependency Injector") limit = int(request.query.get("limit", 10)) gifs = [] return web.json_response( { "query": query, "limit": limit, "gifs": gifs, }, ) Now let's create a container. Container will keep all of the application components and their dependencies. Edit ``containers.py``: .. code-block:: python """Containers module.""" from dependency_injector import containers class Container(containers.DeclarativeContainer): ... Container is empty for now. We will add the providers in the following sections. Finally we need to create ``aiohttp`` application factory. It will create and configure container and ``web.Application``. It is traditionally called ``create_app()``. We will assign ``index`` handler to handle user requests to the root ``/`` of our web application. Put next into the ``application.py``: .. code-block:: python """Application module.""" from aiohttp import web from .containers import Container from . import handlers def create_app() -> web.Application: container = Container() app = web.Application() app.container = container app.add_routes([ web.get("/", handlers.index), ]) return app Now we're ready to run our application Do next in the terminal: .. code-block:: bash adev runserver giphynavigator/application.py --livereload The output should be something like: .. code-block:: bash [18:52:59] Starting aux server at http://localhost:8001 ◆ [18:52:59] Starting dev server at http://localhost:8000 ● Let's check that it works. Open another terminal session and use ``httpie``: .. code-block:: bash http http://127.0.0.1:8000/ You should see: .. code-block:: json HTTP/1.1 200 OK Content-Length: 844 Content-Type: application/json; charset=utf-8 Date: Wed, 29 Jul 2020 21:01:50 GMT Server: Python/3.8 aiohttp/3.6.2 { "gifs": [], "limit": 10, "query": "Dependency Injector" } Minimal application is ready. Let's connect our application with the Giphy API. Giphy API client ---------------- In this section we will integrate our application with the Giphy API. We will create our own API client using ``aiohttp`` client. Create ``giphy.py`` module in the ``giphynavigator`` package: .. code-block:: bash :emphasize-lines: 6 ./ ├── giphynavigator/ │ ├── __init__.py │ ├── application.py │ ├── containers.py │ ├── giphy.py │ └── handlers.py ├── venv/ └── requirements.txt and put next into it: .. code-block:: python """Giphy client module.""" from aiohttp import ClientSession, ClientTimeout class GiphyClient: API_URL = "https://api.giphy.com/v1" def __init__(self, api_key, timeout): self._api_key = api_key self._timeout = ClientTimeout(timeout) async def search(self, query, limit): """Make search API call and return result.""" url = f"{self.API_URL}/gifs/search" params = { "q": query, "api_key": self._api_key, "limit": limit, } async with ClientSession(timeout=self._timeout) as session: async with session.get(url, params=params) as response: if response.status != 200: response.raise_for_status() return await response.json() Now we need to add ``GiphyClient`` into the container. The ``GiphyClient`` has two dependencies that have to be injected: the API key and the request timeout. We will need to use two more providers from the ``dependency_injector.providers`` module: - ``Factory`` provider that will create the ``GiphyClient`` client. - ``Configuration`` provider that will provide the API key and the request timeout. Edit ``containers.py``: .. code-block:: python :emphasize-lines: 3-5,10-16 """Containers module.""" from dependency_injector import containers, providers from . import giphy class Container(containers.DeclarativeContainer): config = providers.Configuration() giphy_client = providers.Factory( giphy.GiphyClient, api_key=config.giphy.api_key, timeout=config.giphy.request_timeout, ) .. note:: We have used the configuration value before it was defined. That's the principle how the ``Configuration`` provider works. Use first, define later. Now let's add the configuration file. We will use YAML. Create an empty file ``config.yml`` in the root root of the project: .. code-block:: bash :emphasize-lines: 9 ./ ├── giphynavigator/ │ ├── __init__.py │ ├── application.py │ ├── containers.py │ ├── giphy.py │ └── handlers.py ├── venv/ ├── config.yml └── requirements.txt and put next into it: .. code-block:: yaml giphy: request_timeout: 10 We will use an environment variable ``GIPHY_API_KEY`` to provide the API key. Now we need to edit ``create_app()`` to make two things when application starts: - Load the configuration file the ``config.yml``. - Load the API key from the ``GIPHY_API_KEY`` environment variable. Edit ``application.py``: .. code-block:: python :emphasize-lines: 11-12 """Application module.""" from aiohttp import web from .containers import Container from . import handlers def create_app() -> web.Application: container = Container() container.config.from_yaml("config.yml") container.config.giphy.api_key.from_env("GIPHY_API_KEY") app = web.Application() app.container = container app.add_routes([ web.get("/", handlers.index), ]) return app Now we need to create an API key and set it to the environment variable. As for now, don’t worry, just take this one: .. code-block:: bash export GIPHY_API_KEY=wBJ2wZG7SRqfrU9nPgPiWvORmloDyuL0 .. note:: To create your own Giphy API key follow this `guide `_. The Giphy API client and the configuration setup is done. Let's proceed to the search service. Search service -------------- Now it's time to add the ``SearchService``. It will: - Perform the search. - Format result data. ``SearchService`` will use ``GiphyClient``. Create ``services.py`` module in the ``giphynavigator`` package: .. code-block:: bash :emphasize-lines: 8 ./ ├── giphynavigator/ │ ├── __init__.py │ ├── application.py │ ├── containers.py │ ├── giphy.py │ ├── handlers.py │ └── services.py ├── venv/ ├── config.yml └── requirements.txt and put next into it: .. code-block:: python """Services module.""" from .giphy import GiphyClient class SearchService: def __init__(self, giphy_client: GiphyClient): self._giphy_client = giphy_client async def search(self, query, limit): """Search for gifs and return formatted data.""" if not query: return [] result = await self._giphy_client.search(query, limit) return [{"url": gif["url"]} for gif in result["data"]] The ``SearchService`` has a dependency on the ``GiphyClient``. This dependency will be injected when we add ``SearchService`` to the container. Edit ``containers.py``: .. code-block:: python :emphasize-lines: 5,18-21 """Containers module.""" from dependency_injector import containers, providers from . import giphy, services class Container(containers.DeclarativeContainer): config = providers.Configuration() giphy_client = providers.Factory( giphy.GiphyClient, api_key=config.giphy.api_key, timeout=config.giphy.request_timeout, ) search_service = providers.Factory( services.SearchService, giphy_client=giphy_client, ) The search service is ready. In next section we're going to put it to work. Make the search work -------------------- Now we are ready to put the search into work. Let's inject ``SearchService`` into the ``index`` handler. We will use :ref:`wiring` feature. Edit ``handlers.py``: .. code-block:: python :emphasize-lines: 4-7,10-14,18 """Handlers module.""" from aiohttp import web from dependency_injector.wiring import Provide, inject from .services import SearchService from .containers import Container @inject async def index( request: web.Request, search_service: SearchService = Provide[Container.search_service], ) -> web.Response: query = request.query.get("query", "Dependency Injector") limit = int(request.query.get("limit", 10)) gifs = await search_service.search(query, limit) return web.json_response( { "query": query, "limit": limit, "gifs": gifs, }, ) To make the injection work we need to wire the container instance with the ``handlers`` module. This needs to be done once. After it's done we can use ``Provide`` markers to specify as many injections as needed for any handler. Edit ``application.py``: .. code-block:: python :emphasize-lines: 13 """Application module.""" from aiohttp import web from .containers import Container from . import handlers def create_app() -> web.Application: container = Container() container.config.from_yaml("config.yml") container.config.giphy.api_key.from_env("GIPHY_API_KEY") container.wire(modules=[handlers]) app = web.Application() app.container = container app.add_routes([ web.get("/", handlers.index), ]) return app Make sure the app is running or use: .. code-block:: bash adev runserver giphynavigator/application.py --livereload and make a request to the API in the terminal: .. code-block:: bash http http://localhost:8000/ query=="wow,it works" limit==5 You should see: .. code-block:: json HTTP/1.1 200 OK Content-Length: 492 Content-Type: application/json; charset=utf-8 Date: Fri, 09 Oct 2020 01:35:48 GMT Server: Python/3.8 aiohttp/3.6.2 { "gifs": [ { "url": "https://giphy.com/gifs/dollyparton-3xIVVMnZfG3KQ9v4Ye" }, { "url": "https://giphy.com/gifs/tennistv-unbelievable-disbelief-cant-believe-UWWJnhHHbpGvZOapEh" }, { "url": "https://giphy.com/gifs/discoverychannel-nugget-gold-rush-rick-ness-KGGPIlnC4hr4u2s3pY" }, { "url": "https://giphy.com/gifs/soulpancake-wow-work-xUe4HVXTPi0wQ2OAJC" }, { "url": "https://giphy.com/gifs/readingrainbow-teamwork-levar-burton-reading-rainbow-3o7qE1EaTWLQGDSabK" } ], "limit": 5, "query": "wow,it works" } .. image:: https://media.giphy.com/media/3oxHQCI8tKXoeW4IBq/source.gif The search works! Make some refactoring --------------------- Our ``index`` handler has two hardcoded config values: - Default search query - Default results limit Let's make some refactoring. We will move these values to the config. Edit ``handlers.py``: .. code-block:: python :emphasize-lines: 14-15,17-18 """Handlers module.""" from aiohttp import web from dependency_injector.wiring import Provide, inject from .services import SearchService from .containers import Container @inject async def index( request: web.Request, search_service: SearchService = Provide[Container.search_service], default_query: str = Provide[Container.config.default.query], default_limit: int = Provide[Container.config.default.limit.as_int()], ) -> web.Response: query = request.query.get("query", default_query) limit = int(request.query.get("limit", default_limit)) gifs = await search_service.search(query, limit) return web.json_response( { "query": query, "limit": limit, "gifs": gifs, }, ) Let's update the config. Edit ``config.yml``: .. code-block:: yaml :emphasize-lines: 3-5 giphy: request_timeout: 10 default: query: "Dependency Injector" limit: 10 The refactoring is done. We've made it cleaner - hardcoded values are now moved to the config. Tests ----- In this section we will add some tests. Create ``tests.py`` module in the ``giphynavigator`` package: .. code-block:: bash :emphasize-lines: 9 ./ ├── giphynavigator/ │ ├── __init__.py │ ├── application.py │ ├── containers.py │ ├── giphy.py │ ├── handlers.py │ ├── services.py │ └── tests.py ├── venv/ ├── config.yml └── requirements.txt and put next into it: .. code-block:: python :emphasize-lines: 32,59,73 """Tests module.""" from unittest import mock import pytest from giphynavigator.application import create_app from giphynavigator.giphy import GiphyClient @pytest.fixture def app(): app = create_app() yield app app.container.unwire() @pytest.fixture def client(app, aiohttp_client, loop): return loop.run_until_complete(aiohttp_client(app)) async def test_index(client, app): giphy_client_mock = mock.AsyncMock(spec=GiphyClient) giphy_client_mock.search.return_value = { "data": [ {"url": "https://giphy.com/gif1.gif"}, {"url": "https://giphy.com/gif2.gif"}, ], } with app.container.giphy_client.override(giphy_client_mock): response = await client.get( "/", params={ "query": "test", "limit": 10, }, ) assert response.status == 200 data = await response.json() assert data == { "query": "test", "limit": 10, "gifs": [ {"url": "https://giphy.com/gif1.gif"}, {"url": "https://giphy.com/gif2.gif"}, ], } async def test_index_no_data(client, app): giphy_client_mock = mock.AsyncMock(spec=GiphyClient) giphy_client_mock.search.return_value = { "data": [], } with app.container.giphy_client.override(giphy_client_mock): response = await client.get("/") assert response.status == 200 data = await response.json() assert data["gifs"] == [] async def test_index_default_params(client, app): giphy_client_mock = mock.AsyncMock(spec=GiphyClient) giphy_client_mock.search.return_value = { "data": [], } with app.container.giphy_client.override(giphy_client_mock): response = await client.get("/") assert response.status == 200 data = await response.json() assert data["query"] == app.container.config.default.query() assert data["limit"] == app.container.config.default.limit() Now let's run it and check the coverage: .. code-block:: bash py.test giphynavigator/tests.py --cov=giphynavigator You should see: .. code-block:: platform darwin -- Python 3.8.3, pytest-5.4.3, py-1.9.0, pluggy-0.13.1 plugins: cov-2.10.0, aiohttp-0.3.0, asyncio-0.14.0 collected 3 items giphynavigator/tests.py ... [100%] ---------- coverage: platform darwin, python 3.8.3-final-0 ----------- Name Stmts Miss Cover --------------------------------------------------- giphynavigator/__init__.py 0 0 100% giphynavigator/application.py 12 0 100% giphynavigator/containers.py 6 0 100% giphynavigator/giphy.py 14 9 36% giphynavigator/handlers.py 10 0 100% giphynavigator/services.py 9 1 89% giphynavigator/tests.py 37 0 100% --------------------------------------------------- TOTAL 88 10 89% .. note:: Take a look at the highlights in the ``tests.py``. It emphasizes the overriding of the ``GiphyClient``. The real API call are mocked. Conclusion ---------- In this tutorial we've built an ``aiohttp`` REST API application following the dependency injection principle. We've used the ``Dependency Injector`` as a dependency injection framework. :ref:`containers` and :ref:`providers` helped to specify how to assemble search service and giphy client. :ref:`configuration-provider` helped to deal with reading YAML file and environment variable. We used :ref:`wiring` feature to inject the dependencies into the ``index()`` handler. :ref:`provider-overriding` feature helped in testing. We kept all the dependencies injected explicitly. This will help when you need to add or change something in future. You can find complete project on the `Github `_. What's next? - Look at the other :ref:`tutorials` - Know more about the :ref:`providers` - Go to the :ref:`contents` .. disqus::