environment/lib/python2.7/site-packages/IPython/core/interactiveshell.py
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.

        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."""

        assert type(exc_tuple)==type(()) , \
               "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
            #print 'Source code    :','\n'.join(self.buffer)
        
        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.
            
            This function will *always* return a list of strings,
            and will raise a TypeError if stb is inappropriate.
            """
            msg = "CustomTB must return list of strings, not %r" % stb
            if stb is None:
                return []
            elif isinstance(stb, basestring):
                return [stb]
            elif not isinstance(stb, list):
                raise TypeError(msg)
            # it's a list
            for line in stb:
                # check every element
                if not isinstance(line, basestring):
                    raise TypeError(msg)
            return stb

        if handler is None:
            wrapped = dummy_handler
        else:
            def wrapped(self,etype,value,tb,tb_offset=None):
                """wrap CustomTB handler, to protect IPython from user code
                
                This makes it harder (but not impossible) for custom exception
                handlers to crash IPython.
                """
                try:
                    stb = handler(self,etype,value,tb,tb_offset=tb_offset)
                    return validate_stb(stb)
                except:
                    # clear custom handler immediately
                    self.set_custom_exc((), None)
                    print >> io.stderr, "Custom TB Handler failed, unregistering"
                    # show the exception in handler first
                    stb = self.InteractiveTB.structured_traceback(*sys.exc_info())
                    print >> io.stdout, self.InteractiveTB.stb2text(stb)
                    print >> io.stdout, "The original exception:"
                    stb = self.InteractiveTB.structured_traceback(
                                            (etype,value,tb), tb_offset=tb_offset
                    )
                return stb

        self.CustomTB = types.MethodType(wrapped,self)
        self.custom_exceptions = exc_tuple
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.

        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."""

        assert type(exc_tuple)==type(()) , \
               "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
            #print 'Source code    :','\n'.join(self.buffer)
        
        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.
            
            This function will *always* return a list of strings,
            and will raise a TypeError if stb is inappropriate.
            """
            msg = "CustomTB must return list of strings, not %r" % stb
            if stb is None:
                return []
            elif isinstance(stb, basestring):
                return [stb]
            elif not isinstance(stb, list):
                raise TypeError(msg)
            # it's a list
            for line in stb:
                # check every element
                if not isinstance(line, basestring):
                    raise TypeError(msg)
            return stb

        if handler is None:
            wrapped = dummy_handler
        else:
            def wrapped(self,etype,value,tb,tb_offset=None):
                """wrap CustomTB handler, to protect IPython from user code
                
                This makes it harder (but not impossible) for custom exception
                handlers to crash IPython.
                """
                try:
                    stb = handler(self,etype,value,tb,tb_offset=tb_offset)
                    return validate_stb(stb)
                except:
                    # clear custom handler immediately
                    self.set_custom_exc((), None)
                    print >> io.stderr, "Custom TB Handler failed, unregistering"
                    # show the exception in handler first
                    stb = self.InteractiveTB.structured_traceback(*sys.exc_info())
                    print >> io.stdout, self.InteractiveTB.stb2text(stb)
                    print >> io.stdout, "The original exception:"
                    stb = self.InteractiveTB.structured_traceback(
                                            (etype,value,tb), tb_offset=tb_offset
                    )
                return stb

        self.CustomTB = types.MethodType(wrapped,self)
        self.custom_exceptions = exc_tuple
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.

        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.