dictionary - Recipe from Python Cookbook -

i'm trying implement recipe o'reilly's python cookbook (2nd ed.) , small portion of recipe doesn't work should. hoping me figure out why.

the recipe "5.14: enhancing dictionary type ratings functionality." i've got of code working, error when trying change 'ranking' of key. i've left in comments author's trying have idea "unders" , "dunders" for. "_rating" aspect, believe somehow causing error.

error:

file "rating.py", line 119, in <module>     r["john"]=20   file "rating.py", line 40, in __setitem__     del self._rating[self.rating(k)]  ## attributeerror: 'ratings' object has no attribute 'rating' 

code:

class ratings(userdict.dictmixin, dict):     '''the implementation mixes inheritance , delegation     achieve reasonable performance while minimizing boilerplate,     and, of course, ensure semantic correctness above.     mappings' methods not implemented below inherited,     dictmixin, but, crucially!, __getitem__ dict. '''      def __init__(self, *args, **kwds):         ''' class gets instantiated 'dict' '''         dict.__init__(self, *args, **kwds)         # self._rating crucial auxiliary data structure: list         # of (value, key) pairs, kept in "natural"ly-sorted order         self._rating = [ (v, k) k, v in dict.iteritems(self) ]         self._rating.sort()      def copy(self):         ''' provide identical independent copy '''         return ratings(self)      def __setitem__(self, k, v):         ''' besides delegating dict, maintain self._rating '''         if k in self:             del self._rating[self.rating(k)]  ##         dict.__setitem__(self, k, v)         insort_left(self._rating, (v, k))      def __delitem__(self, k):         ''' besides delegating dict, maintain self._rating '''         del self._rating[self.rating(k)]         dict.__delitem__(self, k)         ''' delegate methods dict explicitly avoid getting         dictmixin's slower (though correct) implementations instead '''         __len__ = dict.__len__         __contains__ = dict.__contains__         has_key = __contains__         ''' key semantic connection between self._rating , order         of self.keys( ) -- dictmixin gives other methods 'for         free', although implement them directly         better performance. '''          def __iter__(self):             v, k in self._rating:                 yield k             iterkeys = __iter__          def keys(self):             return list(self)          #the 3 ratings-related methods         def rating(self, key):             item = self[key], key             = bisect_left(self._rating, item)             if item == self._rating[i]:                 return             raise lookuperror, "item not found in rating"          def getvaluebyrating(self, rating):             return self._rating[rating][0]          def getkeybyrating(self, rating):             return self._rating[rating][1]          def _test( ):             ''' use doctest test module, must named             rating.py, validating examples in docstrings. '''             import doctest, rating             doctest.testmod(rating)    if __name__ == "__main__":      r = ratings({"bob":30, "john":30})      print "r is"     print r     print "\n"     print "len(r) is"     print len(r)     print "\n"     print "updating {'paul': 20, 'tom': 10} "     r.update({"paul": 20, "tom": 10})     print "\n"     print "now r is"     print r     print "\n"     print "r.has_key('paul') is"     print r.has_key("paul")     print "\n"     print " 'paul' in r is"     print ("paul" in r)     print "\n"     print "r.has_key('alex') is"     print r.has_key("alex")     print "\n"     print " 'alex' in r is"     print ("alex" in r)     print '\n'     print 'r is'     print r     print "changing john '20' 'r['john']= 20' doesn't work. "     r["john"]=20 

your issue indentation. have move following block 1 level left them recognized class methods.

    def __iter__(self):         v, k in self._rating:             yield k         iterkeys = __iter__      def keys(self):         return list(self)      #the 3 ratings-related methods     def rating(self, key):         item = self[key], key         = bisect_left(self._rating, item)         if item == self._rating[i]:             return         raise lookuperror, "item not found in rating"      def getvaluebyrating(self, rating):         return self._rating[rating][0]      def getkeybyrating(self, rating):         return self._rating[rating][1]      def _test( ):         ''' use doctest test module, must named         rating.py, validating examples in docstrings. '''         import doctest, rating         doctest.testmod(rating)         print "doc test?" 

so class be

class ratings(userdict.dictmixin, dict):     '''the implementation mixes inheritance , delegation     achieve reasonable performance while minimizing boilerplate,     and, of course, ensure semantic correctness above.     mappings' methods not implemented below inherited,     dictmixin, but, crucially!, __getitem__ dict. '''      def __init__(self, *args, **kwds):         ''' class gets instantiated 'dict' '''         dict.__init__(self, *args, **kwds)         # self._rating crucial auxiliary data structure: list         # of (value, key) pairs, kept in "natural"ly-sorted order         self._rating = [ (v, k) k, v in dict.iteritems(self) ]         self._rating.sort()      def copy(self):         ''' provide identical independent copy '''         return ratings(self)      def __setitem__(self, k, v):         ''' besides delegating dict, maintain self._rating '''         if k in self:             del self._rating[self.rating(k)]  ##         dict.__setitem__(self, k, v)         insort_left(self._rating, (v, k))      def __delitem__(self, k):         ''' besides delegating dict, maintain self._rating '''         del self._rating[self.rating(k)]         dict.__delitem__(self, k)         ''' delegate methods dict explicitly avoid getting         dictmixin's slower (though correct) implementations instead '''         __len__ = dict.__len__         __contains__ = dict.__contains__         has_key = __contains__         ''' key semantic connection between self._rating , order         of self.keys( ) -- dictmixin gives other methods 'for         free', although implement them directly         better performance. '''      def __iter__(self):         v, k in self._rating:             yield k         iterkeys = __iter__      def keys(self):         return list(self)      #the 3 ratings-related methods     def rating(self, key):         item = self[key], key         = bisect_left(self._rating, item)         if item == self._rating[i]:             return         raise lookuperror, "item not found in rating"      def getvaluebyrating(self, rating):         return self._rating[rating][0]      def getkeybyrating(self, rating):         return self._rating[rating][1]      def _test( ):         ''' use doctest test module, must named         rating.py, validating examples in docstrings. '''         import doctest, rating         doctest.testmod(rating)         print "doc test?"  if __name__ == "__main__":      r = ratings({"bob":30, "john":30})      print "r is"     print r     print "\n"     print "len(r) is"     print len(r)     print "\n"     print "updating {'paul': 20, 'tom': 10} "     r.update({"paul": 20, "tom": 10})     print "\n"     print "now r is"     print r     print "\n"     print "r.has_key('paul') is"     print r.has_key("paul")     print "\n"     print " 'paul' in r is"     print ("paul" in r)     print "\n"     print "r.has_key('alex') is"     print r.has_key("alex")     print "\n"     print " 'alex' in r is"     print ("alex" in r)     print '\n'     print 'r is'     print r     print "changing john '20' 'r['john']= 20' doesn't work. "     r["john"]=20