This article addresses an error encountered when implementing logout functionality in a Python Flask application using the Auth0 Flask Quickstart.

Users may encounter the error when attempting to log out, preventing a successful redirect after logout. 

ServerClient.logout() got an unexpected keyword argument 'return_to'

• Auth0 Python SDK

The error occurs because the auth0.logout() method in the Auth0 Python SDK expects the return_to parameter to be an attribute of an object, not a direct keyword argument. When return_to is passed directly (for example, auth0.logout(return_to='your_url')), the SDK does not recognize it, leading to the unexpected keyword argument error. The correct approach is to encapsulate the return_to URL within a simple object or namespace.

The Auth0 Flask Quickstart document provides the cause of the error and a code snippet to resolve it. 

To resolve this issue, modify how the return_to URL is passed to the auth0.logout() method. Instead of passing it as a direct keyword argument, encapsulate it within an object, such as types.SimpleNamespace. This ensures the SDK correctly interprets the return_to parameter.

Replace the logout function in the Flask application with the following corrected code snippet:

from types import SimpleNamespace
from flask import url_for, redirect

@app.route('/logout')
async def logout():
    """Logout and redirect to Auth0 logout"""
    # Create an object with the 'return_to' attribute
    options = SimpleNamespace(return_to=url_for("index", _external=True))
    logout_url = await auth0.logout(options)
    return redirect(logout_url)