11. ErrorCodes on Flask

Flask's ErrorHandler is used to manage and customize the responses to errors in a Flask application. By default, Flask will display standard error pages for common HTTP errors (e.g., 404 Not Found, 500 Internal Server Error), but you can customize these responses to provide more informative and user-friendly messages.

Here’s an overview of how to handle and customize error responses in Flask:

Handling HTTP Errors

You can handle HTTP errors in Flask by using the @app.errorhandler decorator. This allows you to specify a custom response for a particular HTTP error code.

Example: Handling a 404 Error

In this example, we’ll handle a 404 Not Found error by displaying a custom error page.

Create a Flask Application:

from flask import Flask, render_template

app = Flask(__name__)

Create an Error Handler:

@app.errorhandler(404)
def page_not_found(e):
    return render_template('404.html'), 404

Create a 404 Template: In the templates directory, create a 404.html file with custom content for the 404 error page.

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Page Not Found</title>
  </head>
  <body>
    <h1>Page Not Found</h1>
    <p>Sorry, but the page you were trying to view does not exist.</p>
  </body>
</html>

Run the Application:

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

Example: Handling a 500 Error

Similarly, you can handle a 500 Internal Server Error by creating another error handler:

Create an Error Handler:

@app.errorhandler(500)
def internal_error(e):
    return render_template('500.html'), 500

Create a 500 Template: In the templates directory, create a 500.html file with custom content for the 500 error page.

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Internal Server Error</title>
  </head>
  <body>
    <h1>Internal Server Error</h1>
    <p>Sorry, but there was an internal server error. Please try again later.</p>
  </body>
</html>

Example: Handling Multiple Errors

You can handle multiple errors by defining multiple error handlers:

Define Error Handlers:

@app.errorhandler(404)
def page_not_found(e):
    return render_template('404.html'), 404

@app.errorhandler(500)
def internal_error(e):
    return render_template('500.html'), 500

@app.errorhandler(403)
def forbidden(e):
    return render_template('403.html'), 403

Create Templates: Create 404.html, 500.html, and 403.html in the templates directory with custom content for each error.

Example: Using Blueprints for Error Handling

If you are using Blueprints, you can define error handlers within the Blueprint:

Create a Blueprint:

from flask import Blueprint, render_template

errors = Blueprint('errors', __name__)

@errors.app_errorhandler(404)
def page_not_found(e):
    return render_template('404.html'), 404

@errors.app_errorhandler(500)
def internal_error(e):
    return render_template('500.html'), 500

Register the Blueprint:

from flask import Flask
from errors import errors

app = Flask(__name__)
app.register_blueprint(errors)

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

By customizing error handlers in Flask, you can provide more meaningful feedback to users and improve the overall user experience of your web application.

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Last updated 1 year ago