# 8.5 User-defined Exceptions

Programs may name their own exceptions by assigning a string to a variable. For example:

    >>> my_exc = 'my_exc'
    >>> try:
    ...     raise my_exc, 2*2
    ... except my_exc, val:
    ...     print 'My exception occurred, value:', val
    ...
    My exception occurred, value: 4
    >>> raise my_exc, 1
    Traceback (innermost last):
      File "<stdin>", line 1
    my_exc: 1
    >>>

Many standard modules use this to report errors that may occur in functions they define.