Implement 'k in s' more cleanly and add doctest.

IPython/ipstruct.py

@@ -163,8 +163,22 b' class Struct:'
         return self.__dict__[key]
 
     def __contains__(self,key):
-        """Allows use of the 'in' operator."""
-        return self.__dict__.has_key(key)
+        """Allows use of the 'in' operator.
+
+        Examples:
+        >>> s = Struct(x=1)
+        >>> 'x' in s
+        True
+        >>> 'y' in s
+        False
+        >>> s[4] = None
+        >>> 4 in s
+        True
+        >>> s.z = None
+        >>> 'z' in s
+        True
+        """
+        return key in self.__dict__
 
     def __iadd__(self,other):
         """S += S2 is a shorthand for S.merge(S2)."""
@@ -246,12 +260,13 b' class Struct:'
         Optionally, one or more key=value pairs can be given at the end for
         direct update."""
 
-        # The funny name __loc_data__ is to prevent a common variable name which
-        # could be a fieled of a Struct to collide with this parameter. The problem
-        # would arise if the function is called with a keyword with this same name
-        # that a user means to add as a Struct field.
+        # The funny name __loc_data__ is to prevent a common variable name
+        # which could be a fieled of a Struct to collide with this
+        # parameter. The problem would arise if the function is called with a
+        # keyword with this same name that a user means to add as a Struct
+        # field.
         newdict = Struct.__make_dict(self,__loc_data__,**kw)
-        for k,v in newdict.items():
+        for k,v in newdict.iteritems():
             self[k] = v
 
     def merge(self,__loc_data__=None,__conflict_solve=None,**kw):