sqlalchemy.exc.InvalidRequestError: Object '<User at 0x7fbe82f13be0>' is already attached to session 'n'

[Kamalkoranga]

I've getting error in deleting user.

while using cascade too...

Route for deleting user is :

[GmGniap]

I think if you're running on MacOS , change port number to greater than default 5000.
In your server.py script , change as below.

if __name__ == "__main__":
    app.run(port= 8000, debug=True)

I hope it'll solve your problem. Reference