>>> from enthought.traits.api import HasTraits, Str, Trait 
>>> class InventoryItem(HasTraits):
...    name  = Str # String value, default is ''
...    stock = Trait(None, 0, 1, 2, 3, 'many')
...            # Enumerated list, default value is 
...            #'None'
... 
>>> hats = InventoryItem()
>>> hats.name = 'Stetson'

>>> print '%s: %s' % (hats.name, hats.stock)
Stetson: None

>>> hats.stock = 2      # OK
>>> hats.stock = 'many' # OK
>>> hats.stock = 4      # Error, value is not in \
>>>                     # permitted list 
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "c:\wrk\src\lib\enthought\traits\trait_handlers.py", line 
90, in error
    raise TraitError, ( object, name, self.info(), value )
enthought.traits.trait_errors.TraitError: The 'stock' trait of an 
InventoryItem instance must be None or 0 or 1 or 2 or 3 or 
'many', but a value of 4 was specified.
