What is Flask?

Flask is a microweb framework that provides a simple and easy-to-use interface for building web applications. It is built on top of the Werkzeug WSGI library and Jinja2 template engine, and it has a small and easy-to-extend core. Flask is a popular choice for building web applications because it is lightweight, easy to use, and scalable.

Setting up Flask

To use Flask, you will need to have Python and pip (the Python package manager) installed on your machine. If you don’t already have these, you can download Python from the Python website and install pip using the following command:

python -m ensurepip --upgrade

Once you have Python and pip installed, you can install Flask using pip. Open a terminal and enter the following command:

pip install flask

This will install Flask and all of its dependencies.

Creating a Flask application

Now that you have Flask installed, you are ready to create your first Flask application. To do this, you will need to create a new Python file and import the Flask module.

from flask import Flask

app = Flask(__name__)

The Flask object is the main entry point for the Flask application. You can create a Flask object by passing the name of the current module (name) as an argument.

Next, you will need to define a route and a view function. A route is a URL pattern that is mapped to a function, and a view function is a Python function that returns a response to the client.

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

In this example, we have defined a route at the root URL (‘/’) and a view function that returns the string ‘Hello, World!’.

To run the application, you will need to call the run() method of the Flask object. Add the following line to the bottom of your Python file:

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

This will start the Flask development server and make your application available at http://localhost:5000.

Testing the application

To test your application, open a web browser and navigate to http://localhost:5000. You should see the message ‘Hello, World!’ displayed in the browser.

Congratulations! You have successfully set up Flask and created a simple “Hello, World” application. From here, you can start building more complex applications by adding more routes and view functions, as well as using templates and static files.

For more information on Flask, be sure to check out the Flask documentation, which provides detailed instructions on how to use the framework and build web applications with it. Good luck with your Flask journey!