[Python-Dev] bool does not want to be subclassed?

[Guido van Rossum]

> Type objects are also singletons (e.g., type(True) returns the same object
> as type(False); ditto type("True") and type("False") and type("xyz"); etc).

But types are not immutable, so their semantics are different anyway.
The point of the remark was to emphasize that immutable types have
some leniency in their semantics regarding object identity.  For
mutable types the semantics regarding object identity are defined
explicitly by each type or operation (some operations always return a
new object, others always return the same one).

--Guido van Rossum (home page: http://www.python.org/~guido/)