Method set_custom_exc

IPython/core/interactiveshell.py:1987–2088

set_custom_exc(exc_tuple, handler) Set a custom exception handler, which will be called if any of the exceptions in exc_tuple occur in the mainloop (specifically, in the run_code() method). Parameters ---------- exc_tuple : tuple of exception classes

(self, exc_tuple, handler)

        self.InteractiveTB.set_mode(mode=self.xmode)

    def set_custom_exc(self, exc_tuple, handler):
        """set_custom_exc(exc_tuple, handler)

        Set a custom exception handler, which will be called if any of the
        exceptions in exc_tuple occur in the mainloop (specifically, in the
        run_code() method).

        Parameters
        ----------
        exc_tuple : tuple of exception classes
            A *tuple* of exception classes, for which to call the defined
            handler.  It is very important that you use a tuple, and NOT A
            LIST here, because of the way Python's except statement works.  If
            you only want to trap a single exception, use a singleton tuple::

                exc_tuple == (MyCustomException,)

        handler : callable
            handler must have the following signature::

                def my_handler(self, etype, value, tb, tb_offset=None):
                    ...
                    return structured_traceback

            Your handler must return a structured traceback (a list of strings),
            or None.

            This will be made into an instance method (via types.MethodType)
            of IPython itself, and it will be called if any of the exceptions
            listed in the exc_tuple are caught. If the handler is None, an
            internal basic one is used, which just prints basic info.

            To protect IPython from crashes, if your handler ever raises an
            exception or returns an invalid result, it will be immediately
            disabled.

        Notes
        -----
        WARNING: by putting in your own exception handler into IPython's main
        execution loop, you run a very good chance of nasty crashes.  This
        facility should only be used if you really know what you are doing.
        """

        if not isinstance(exc_tuple, tuple):
            raise TypeError("The custom exceptions must be given as a tuple.")

        def dummy_handler(self, etype, value, tb, tb_offset=None):
            print('*** Simple custom exception handler ***')
            print('Exception type :', etype)
            print('Exception value:', value)
            print('Traceback      :', tb)

        def validate_stb(stb):
            """validate structured traceback return type

            return type of CustomTB *should* be a list of strings, but allow
            single strings or None, which are harmless.