python - Construct a object which can be mapped or un packed -

so have (of course true thing more complicated) :

class test(object):     = -1      def keys(self):         return ["a", "b"]      def __getitem__(self, item):         return {"a": 0, "b": 1}[item]      def __len__(self):         return 2      def __contains__(self, item):         if item in ["a", "b"]:             return true         return false      def __iter__(self):         return self      def next(self):         self.i += 1         if self.i > 1:             raise stopiteration()          return ["a", "b"][self.i] 

what want (again true thing more complex):

> t = test() > dict(t)  {'a': 0, 'b': 1} > dict(**t)   {'a': 0, 'b': 1} 

this work perfectly, fail work if define class subclass of dict, , want, want object behave dict hidden tricks under knees (and again sure makes more sense in real code):

class test(dict):      .... same code here .... 

in case dict(t) , dict(**t) return empty dictionary {}, [k k in t] return ['a','b'].

what miss ? seems need redeclare dict function, though __getitem__, __iter__, __len__, __contains__ , keys method enough trick. tried redeclare iterkeys, itervalues, copy, get, etc, nothing seems work.

thanks.

 class test(dict):     = -1      def __init__(self):         super(test, self).__init__({"a": 0, "b": 1})      def keys(self):         return ["a", "b"]      def __getitem__(self, item):         return {"a": 0, "b": 1}[item]      def __len__(self):         return 2      def __contains__(self, item):         if item in ["a", "b"]:             return true         return false      def __iter__(self):         return self      def next(self):         self.i += 1         if self.i > 1:             raise stopiteration()          return ["a", "b"][self.i]  t = test() print dict(t) # output: {'a': 0, 'b': 1} print dict(**t) # output: {'a': 0, 'b': 1} 

of course, hardcode {'a': 0, 'b': 1} in class definition not idea.