1st Sketch at at ReadOnly dict

[Charles Hixson]

This is just a first sketch, and I haven't yet attempted to test it, so 
what I'm hoping for is criticisms on the general approach.

##    Read Only dict class.
#    @note Instances can be created only from existing dicts.
#    @warning    values within the RODict can be accessed, so if they hold
#            references to other items, they can be altered.
class RODict:
     #Instance Variable Doc
     ##    @var    _ddict
     #        This variable holds the reference to the dict.

     ##    Class initializer.
     #    @param    ddict    The data dictionary to which this is a read 
only
     #            access.
     #    @throws    TypeError if ddict is not a dict.
     def __init__ (self, ddict = {}):
         if not isinstance(ddict, dict):
             raise    TypeError("ddict must be a dict.  It is " + 
repr(ddict))
         self._ddict    =    ddict

     ##    Test for containment.
     #    @param    key    The item to be found.
     #    @return    True    If key is in the instance, otherwise False.
     def __contains__(self, key):
         return    key in self._ddict

     ##    Pass along the __getitem call.
     def __getitem__(self, key):
         return    self._ddict.__getitem__(key)

     ##    Pass along the get call.
     def get (self, key, default = None):
         return    self._ddict.get(key, default)

     ##    Return a DictView of the items of the instance.
     def items(self):
         return    self._ddict.items()

     ##    Return a DictView of the keys of the instance.
     def keys(self):
         return    self._ddict.keys()

     ##    Return a DictView of the values of the instance.
     def values(self):
         return    self._ddict.values()


     ##    Return the length of the dict.
     def __len__(self):
         return    len(self._ddict)

-- 
Charles Hixson