[$] Python sets, frozensets, and literals

A Python "frozenset" is simply a setobject that is immutable-the objects it contains are determined atinitialization time and cannot be changed thereafter. Like sets, frozensets arebuilt into the language, but unlike most of the other standard Pythontypes, there is no way to create a literal frozenset object. Changing that,by providing a mechanism to do so, was the topic of a recent discussion on the python-ideas mailing list.