Creating our own exceptions

The hierarchy of exceptions has a superclass for error-related exceptions, called Exception. All of the exceptions which reflect essentially erroneous conditions are subclasses of the Exception class. The base class for all exceptions is the BaseException class; some non-error-related exceptions are direct subclasses of the BaseException class.

We can summarize the hierarchy like this:

• BaseException

  • SystemExit

  • KeyboardInterrupt

  • GeneratorExit

  • Exception

    • All other exceptions

The superclass of all error-related exceptions, Exception, is quite broad. We can use this in a long-running server like this:

def server():
        try:
        while True:
            try:
                one_request()
            except Exception as e:
                print(e.__class__.__name__, e)
    except Shutdown_Request:
        print("Shutting Down")

This example depends on a function, one_request(), which handles a single request. The while loop runs forever, evaluating the one_request...