Built-in Exception Classes

I didn’t really pull the prior section’s examples out of thin air. All built-in exceptions that Python itself may raise are predefined class objects. Moreover, they are organized into a shallow hierarchy with general superclass categories and specific subclass types, much like the exceptions class tree we developed earlier.

In Python 3.0, all the familiar exceptions you’ve seen (e.g., SyntaxError) are really just predefined classes, available as built-in names in the module named builtins (in Python 2.6, they instead live in __builtin__ and are also attributes of the standard library module exceptions). In addition, Python organizes the built-in exceptions into a hierarchy, to support a variety of catching modes. For example: