From the definition, e is the parameter of page_not_found, and e may be an instance of Exception, which can be identified by
type(e).

You will know if you try without writing e. The foundation is not solid. . .

I saw this place too. See it from this Chinese document

An error handler is a function similar to a view function, but it is executed when an error occurs, and the error is passed in as a parameter. Generally the error will be an HTTPException , but in some cases it will be other errors: the internal server's error handler will be executed with the actual code error being caught as a parameter.

This littleecan be an error caused by HTTP or other errors (thank you for the reminder).

e is an error object. The error information is stored in this variable, similar to:

try: eat() except Exception as e: print(e)