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Add a piece of the tutorial
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Flask tutorial
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==============
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Coming soon...
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This tutorials shows how to build ``Flask`` application following dependency injection principle.
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What are we going to build?
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---------------------------
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We will build a web application that helps to search for repositories on Github. Let's call it
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Github Navigator.
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How does Github Navigator work?
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- User opens a web page that asks to provide a search term.
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- User types the search term and hits Enter.
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- Github Navigator takes that and searches through the Github for matching repositories.
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- When search is done Github Navigator returns user a web page with the result.
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- The results page shows all matching repositories and the provided search term.
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- For any matching repository user sees:
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- the repository name
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- the owner of the repository
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- the last commit to the repository
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- User can click on the repository, the repository owner or the last commit to open its web page
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on the Github.
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Prepare the environment
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-----------------------
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Let's create the environment for the project.
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First we need to create a project folder and the virtual environment:
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.. code-block:: bash
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mkdir ghnav-flask-tutorial
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cd ghnav-flask-tutorial
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python3 -m venv venv
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Now let's activate the virtual environment:
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.. code-block:: bash
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. venv/bin/activate
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Project layout
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--------------
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Environment is ready and now we're going to create the layout of the project.
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Create next structure in the current directory. All files should be empty. That's ok for now.
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Initial project layout::
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./
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├── githubnavigator/
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│ ├── __init__.py
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│ ├── application.py
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│ ├── containers.py
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│ └── views.py
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├── venv/
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└requirements.txt
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Now it's time to install ``Flask`` and ``Dependency Injector``.
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Put next lines to the ``requirements.txt`` file::
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flask
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dependency-injector
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Now let's install it::
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pip install -r requirements.txt
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And check that installation is successful::
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python -c "import flask; print(flask.__version__)"
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python -c "import dependency_injector; print(dependency_injector.__version__)"
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You should see something like::
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(venv) $ python -c "import flask; print(flask.__version__)"
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1.1.2
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(venv) $ python -c "import dependency_injector; print(dependency_injector.__version__)"
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3.22.0
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*Versions can be different. That's fine.*
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Hello world!
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------------
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Let's create minimal application.
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Put next to the ``views.py``:
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.. code-block:: python
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"""Views module."""
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def index():
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return 'Hello, World!'
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Ok, we have the view.
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Now let's create the heart of our application - the container. Container will keep all of the
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application components and their dependencies. First two providers we need to add are
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the ``Flask`` application provider and the view provider.
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Put next to the ``containers.py``:
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.. code-block:: python
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"""Application containers module."""
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from dependency_injector import containers
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from dependency_injector.ext import flask
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from flask import Flask
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from . import views
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class ApplicationContainer(containers.DeclarativeContainer):
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"""Application container."""
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app = flask.Application(Flask, __name__)
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index_view = flask.View(views.index)
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Finally we need to create the Flask application factory. It is traditionally called
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``create_app()``. It will create the container. After that it will use the container to create
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the Flask application. Last step is to configure the routing - we will assign ``index_view`` from the
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container to handle user requests to the root ``/`` if our web application.
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Put next to the ``application.py``:
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.. code-block:: python
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"""Application module."""
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from .containers import ApplicationContainer
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def create_app():
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"""Create and return Flask application."""
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container = ApplicationContainer()
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app = container.app()
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app.container = container
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app.add_url_rule('/', view_func=container.index_view.as_view())
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return app
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.. note::
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Container is the first object in the application.
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The container is used to create all other components.
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Ok. Now we're ready to say "Hello, World!".
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Do next in the terminal::
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export FLASK_APP=githubnavigator.application
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export FLASK_ENV=development
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flask run
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The output should be something like::
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* Serving Flask app "githubnavigator.application" (lazy loading)
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* Environment: development
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* Debug mode: on
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* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
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* Restarting with fsevents reloader
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* Debugger is active!
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* Debugger PIN: 473-587-859
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Open your browser and go to the ``http://127.0.0.1:5000/``.
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You should see ``Hello, World!``.
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That's it. Our minimal application is up and running.
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