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Build your web app from scratch: Flask installation and configuration guide

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Feb 23, 2024 pm 05:45 PM

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Build your web app from scratch: Flask installation and configuration guide

Flask Installation and Configuration Guide: Build your Web application from scratch, specific code examples are required

Introduction:
Flask is a lightweight Python Web framework, it is very suitable for beginners. This article will take you from scratch, introduce how to install and configure Flask, and show some specific code examples to help you build your own web application.

1. Install Flask:
First, make sure Python is installed on your machine. We can then install Flask by using pip (Python’s package management tool). Open a command line terminal and run the following command:

pip install flask

2. Create a Flask application:
After completing the Flask installation, we can create a new Flask application. First, create a new folder to store your project files. Then, create a Python file named app.py under the folder. Switch to the folder directory in Terminal and open the app.py file using your favorite text editor.

3. Import the Flask module:
In the app.py file, we need to import the Flask module to use its functions. Add the following code at the beginning of the file:

from flask import Flask
app = Flask(__name__)

The above code will import the Flask module and create a Flask application object named app.

4. Write view functions:
The main component of the Flask application is the view function. View functions are used to respond to user requests and return corresponding content. In the app.py file, we can write a simple view function. The following is an example:

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

The above code defines a view function, the function name is hello_world, and its URL address is /. When the user accesses the root directory of the website, the view function will be executed and the string 'Hello, World!' will be returned as the response content.

5. Run the Flask application:
Add the following code at the end of the app.py file to run the Flask application:

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

The above code will start a local development server and run the Flask application. You can use a browser to visit http://localhost:5000 and see the words 'Hello, World!'.

6. Add more routing and view functions:
A Flask application can contain multiple routing and view functions. We can add more routes and view functions as needed. The following is an example:

@app.route('/about')
def about():
    return 'About page'

@app.route('/contact')
def contact():
    return 'Contact page'

The above code defines two new view functions, corresponding to the URLs of /about and /contact respectively. When users access these URLs, the corresponding view functions will be executed and the corresponding content will be returned.

7. Template rendering:
Flask can also use the template engine to render dynamic content into HTML pages. First, we need to create a folder named templates under the project folder to store HTML template files. Then, create a file named index.html under the template folder and add the following content:

<!DOCTYPE html>
<html>
<head>
    <title>Flask Web App</title>
</head>
<body>
    <h1 id="message">{{ message }}</h1>
</body>
</html>

In the app.py file, we can Use Flask's render_template function to render the template. Here is an example:

from flask import render_template

@app.route('/greeting')
def greeting():
    return render_template('index.html', message='Welcome to Flask Web App')

The above code defines a view function named greeting that will render index when the user accesses /greeting. html template, and pass in the value of variable message.

8. Run the Flask application:
Run the app.py file and use the browser to access the corresponding URL. You will see that the dynamic content in the template is rendered correctly.

Summary:
This article introduces how to install and configure Flask, and gives some specific code examples to help you build your own web application from scratch. I hope this article will be helpful for you to learn Flask. Good luck writing great web applications!

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