Hello! Today we want to talk about a new and functional method in the Flask framework. This method is called call_on_close() and has been added in version 3.0 of this framework. First of all, we should mention that Flask is one of the most popular frameworks for developing web applications in Python. This method allows you to add functionalities that can be executed after a request has been closed.
Therefore, let's assume we have a web application that needs to perform a specific task after completing a request, such as saving information to a database or performing calculations. By using call_on_close(), we can easily accomplish these tasks without needing to add more lines of code in other parts of the application.
This method allows us to add new functionalities to the request processing flow. It's similar to a callback that gets executed after the lifecycle of a Flask request ends. It can really simplify the developers' work.
How can we use call_on_close()?
Now that we know call_on_close() is possible, let’s move on to how to use it. In the following example, we'll create a simple Flask application and use this method to print a message in the console after each request.
from flask import Flask
app = Flask(__name__)
@app.route('/')
def home():
return "Hello to Flask!"
# A function that will be executed after the request is closed
def after_request():
print("Request completed!")
# Adding the function to call_on_close
app.call_on_close(after_request)
if __name__ == '__main__':
app.run(debug=True)
Line by Line Explanation about the Code
from flask import Flask
At the beginning of the code, we import Flask from the flask module.
app = Flask(__name__)
This line creates an instance of the Flask class to use as our application.
@app.route('/'):
This decorator defines the main route for the application, meaning when a request is made to the root URL, this function will execute.
def home():
This function simply returns a plain text response.
def after_request():
This function runs after every completed request and prints a message in the console.
app.call_on_close(after_request)
This line adds the 'after_request' function to the list of functions to be executed after the request is closed.
app.run(debug=True)
Finally, we run the application in debug mode.