A small number of constants live in the built-in namespace. They are:
False
The false value of the bool type.
New in version 2.3.
True
The true value of the bool type.
New in version 2.3.
None
The sole value of types.NoneType. None is
frequently used to represent the absence of a value, as when default
arguments are not passed to a function.
NotImplemented
Special value which can be returned by the ``rich comparison''
special methods (__eq__(), __lt__(), and friends),
to indicate that the comparison is not implemented with respect to
the other type.
Ellipsis
Special value used in conjunction with extended slicing syntax.
