Built-in exceptions are all named with a leading upper-case letter. This makes them consistent with class names, which also begin with a leading upper-case letter.

Most modules or classes will have a single built-in exception, often called Error. This exception will be imported from a module, and can then be qualified by the module name. Modules and module qualification is covered in Part IV, “Components, Modules and Packages”. It is not typical to have a complex hierarchy of exceptional conditions defined by a module.