attribute(attrname, permit='rwd', fget=None, fset=None, fdel=None, doc='')

returns a property associated with 'attrname'.

By default, a simple property with get, set, and delete methods
will be created. Optionally, specific get/set/del methods may be
supplied. You can also choose to omit the creation of one or more
of the default get/set/del methods via the 'permit' flag:
    'r': readable, 'w':writable, 'd':deletable
So, if you want a property that is readable and deletable, but not
writable, use "permit='rd'".