Structure Your Project with Flask Blueprint

Flask is a lightweight WSGI web application framework based on Python. It is designed in such a way that it will only supply the core components of a web application and it lets the developer choose rest of the things. It leaves all the design and architecture level decisions to the developer.

As a result it is very easy to get started start with Flask. But day by day when the application gets bigger and more complex, it become very tough to maintain the code base. To resolve this problem Flask comes with Blueprint.

Flask Blueprint or Blueprint for short, is a way to organize the related code base between python modules or packages. In this article we will learn how to use Blueprint to structure a Flask project.

At the beginning, lets first create a hello world application in Flask. Create a file app.py and put the following code in it.

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

if __name__ == '__main__':
    app.run(debug=True)

What we have done here is that, first we have created an Flask application object by passing the name of the application’s module or package. Then we define a function hello_world and associates it with '/' url endpoint using route decorator of the app object.

Now open up your terminal and write this command python app.py and hit enter. It will run your application on port 5000 of your machine.

While the application is running, go to http://localhost:5000 in your favorite browser and see that Hello, World! is printed on it.

As your basic Flask application is up and running. Now create a new file views.py and write the following code in it.

from flask import Blueprint

index_blueprint = Blueprint('index_blueprint', __name__)

@index_blueprint.route('/index/')
def index():
    return 'This is flask blueprint example'

Here we have done the following things.

• We import Blueprint from flask.
• Created a Blueprint object and name it index_blueprint.
• And associates our index function with /index/ url endpoint using route decorator of index_blueprint.

While creating the index_blueprint object, first we have passed the name of the blueprint that will be used in Flask’s routing mechanism. And then we have passed __name__ as the second argument which will be used by Flask to locate the Blueprint’s resources.

Now that we have our blueprint object, we need to register it with app object. The following code base shows how to register index_blueprint with app object in app.py file.

from views import index_blueprint

app = Flask(__name__)
app.register_blueprint(index_blueprint)

app.register_blueprint is the method we used here to register the blueprint with the app object.

As we have registered our blueprint with the application, it’s time to check if our blueprint is actually working.

To check that open your terminal and run this command python app.py, then go to http://localhost/index/ in your browser and see that This is flask blueprint example is printed.

We have successfully used Flask Blueprint in our project and we have structured our project in different python modules using the Blueprint.

When the project will grow bigger and bigger that time we can adopt the following project structure to keep it more maintainable.

project_root/
|
|--app.py
|--app_module/
    |
    |--__init__.py
    |--views.py

The complete code of this article can be found at this repository.