How To Create Your First Web Application Using Flask and Python 3

Seeing how this view is supposed to be part of a backend API that sends and receives JSON, the response body must be JSON serializable. Ensure that it's ready for transmission by calling json.dumps on your dictionary, which will turn your Python object into valid JSON. This is used instead of jsonify, as jsonify constructs an actual response object using its input as the response body. In contrast, json.dumps just takes a given Python object and converts it into a valid JSON string if possible. The flask-sqlalchemy package leverages SQLAlchemy to set up and inform the database structure.

  • The main structure of base.html is similar to a normal HTML page.
  • If you're building a high-performance, data-intensive API that needs to handle a large volume of requests with minimal overhead, FastAPI is likely the better choice.
  • In Flask, a configuration is done on an attribute named config of the Flask object.
  • In this recipe, we'll take the application from the previous recipe, Composition of views and models, as a reference and modify it to work using blueprints.

To overcome this, the debug support is enabled so as to track any error. Knowing these facts about working with Flask views allows you to construct a view whose job is to create new Task objects. Finally, any response you want from a view that's more complex than a string must be built deliberately.

HTML and CSS for Python Developers

We no longer need the application object anymore, and our complete routing is defined on a blueprint named hello. The same blueprint is imported into flask_app/my_app/ and registered on the application object. For first-time readers, Flask is a lightweight web application microframework written in Python. It makes use of the flexibility of Python to provide a relatively simple template for web application development. Flask makes it possible to write simple one-page applications, but it also has the power to scale them and build larger applications without any issues. Flask, being a well-established framework in the Python web development ecosystem, boasts a vast and thriving community with a rich collection of extensions, libraries, and resources.

This environment will include both the Flask web application development framework and the Python programming language. In the preceding script, most of the configuration is self-explanatory. The classifiers are used when the application is made available on PyPI. These will help other users search the application using the relevant classifiers.

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Similar to the Django web framework, it handles templates in a sandbox. The microframework Flask is part of the Pallets Projects (formerly Pocoo), and based on several others of them, all under a BSD license. This working Flask web project is a great starting point for any future Flask projects that you may have. By understanding these foundational flask developer concepts, you’re now well equipped to tackle more complex projects and further explore the capabilities of Flask. In the next section, you’ll leverage template inheritance to add consistent styling to your web project. Instead of adding the navigation menu code directly into base.html, you include _navigation.html in your website’s header.

flask framework in python

Also make sure to include a keyword argument (back_populates) that updates the User model when the task gets a user as an owner. In a given web application, you may want to be able to express relationships between objects. In the To-Do List example, users own multiple tasks, and each task is owned by only one user. This is an example of a "many-to-one" relationship, also known as a foreign key relationship, where the tasks are the "many" and the user owning those tasks is the "one." Flask needs the database URL to be part of its central configuration through the SQLALCHEMY_DATABASE_URI attribute.

Step 1 — Installing Flask

To see the benefits of an application factory in action, you’ll create your first blueprint in the next section. If you enter a different name than flask or python-flask, you will need to specify this name when using the commands that we will create later. The previous recipe, Composition of views and models, is useful for further understanding how this recipe is useful. The following is an example of a simple Hello World application using Blueprint.

  • Flask doesn't come with its own database-management utility, so you'll have to write your own (to some degree).
  • Included templates are partials that contain a fraction of the full HTML code.
  • Presenting this information to the users in an interactive fashion adds a lot of value to the application.
  • By default, Flask expects your templates to be in a templates/ directory.
  • The file allows you to import from todo as if it were an installed package.
  • With some minimal styling, your Flask web project is starting to look like a finished web app.

It is simple to use and comprehend, so you can get started designing web applications straight away. An interesting way of laying out configurations for different deployment modes, such as production, testing, staging, and so on, can be cleanly done using the inheritance pattern of classes. In this recipe, we will learn how to use class-based settings to achieve such a pattern.

Step 6 — Debugging A Flask Application

Within the todo directory containing your source code, create an file and a blank file. The file allows you to import from todo as if it were an installed package. This is where all the Flask application goodness will go, and you'll create an environment variable that points to that file. If you're using pipenv (like I am), you can locate your virtual environment with pipenv –venv and set up that environment variable in your environment's activate script. You’ve also learned how to use dynamic routes to allow users to interact with your web application via the URL, and how to use the debugger to troubleshoot errors. In this tutorial, you’ll build a small web application that renders HTML text on the browser.

flask framework in python

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