http://www.python.org/dev/peps/pep-3106/ http://www.python.org/dev/peps/pep-3106/ The original plan was to simply let .keys(), .values() and .items() retur

http://www.python.org/dev/peps/pep-3106/ http://www.python.org/dev/peps/pep-3106/ The original plan was to simply let .keys(), .values() and .items() return an iterator, i.e. exactly what iterkeys(), itervalues() and iteritems() return in Python 2.x. However, the Java Collections Framework [1] suggests that a better solution is possible: the methods return objects with set behavior (for .keys() and .items()) or multiset (== bag) behavior (for .values()) that do not contain copies of the keys, values or items, but rather reference the underlying dict and pull their values out of the dict as needed.