Flask is a popular web framework for building web applications in Python. It is lightweight, easy to use, and flexible, making it a great choice for developers looking to create web applications quickly and efficiently. In this tutorial, we will cover the basics of Flask and show you how to get started building your first web application.
Installation:
The first step to getting started with Flask is to install it on your system. Flask can be installed using the Python package manager pip. Simply run the following command in your terminal to install Flask:
pip install FlaskCreating a basic Flask application:
Once Flask is installed, you can start building your first web application. Create a new Python file (app.py) and add the following code to create a basic Flask application:
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello, World!'
if __name__ == '__main__':
app.run()This code creates a new Flask application and defines a route to the root URL ("/") that returns the string "Hello, World!". To run the Flask application, simply execute the Python file using the following command:
python app.pyYou should see a message indicating that the Flask application is running on localhost:5000. Open a web browser and navigate to http://localhost:5000 to see the "Hello, World!" message displayed on the page.
Routing:
Flask uses routing to map URLs to Python functions that handle requests. You can define routes by using the @app.route() decorator. Routes can also include variable parameters that can be accessed within the Python function. Here is an example of defining a route with a variable parameter:
@app.route('/user/<username>')
def show_user_profile(username):
return 'User %s' % usernameIn this example, the route "/user/show_user_profile() function.
Templates:
Flask uses Jinja2 templates to generate HTML content dynamically. Templates allow you to separate the presentation layer from the business logic of your application. Create a new folder called "templates" in your project directory and add a new template file (index.html) with the following content:
<!DOCTYPE html>
<html>
<head>
<title>Flask App</title>
</head>
<body>
<h1>Hello, {{ name }}</h1>
</body>
</html>Update the original Flask application code to render the template:
from flask import Flask, render_template
app = Flask(__name__)
@app.route('/')
def hello_world():
return render_template('index.html', name='World')
if __name__ == '__main__':
app.run()In this revised code, the render_template() function is used to render the index.html template and pass a variable called "name" with the value ‘World’.
Static files:
Flask also allows you to serve static files such as CSS, JavaScript, and images. Create a new folder called "static" in your project directory and add your static files to this folder. You can link to static files in your templates using the url_for() function. Here’s an example of linking to a CSS file in a template:
<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">To add support for static files in your Flask application, update the app.run() function in your Python code as follows:
if __name__ == '__main__':
app.run(debug=True)This will enable Flask to serve static files in debug mode.
Conclusion:
Flask is a powerful web framework that makes it easy to build web applications in Python. In this tutorial, we covered the basics of Flask, including how to install it, create routes, use templates, and serve static files. With this knowledge, you can start building your own web applications using Flask and take advantage of its flexibility and simplicity. Happy coding!
