A small number of constants live in the built-in namespace. They are:
\begin{datadesc}{False}
The false value of the \class{bool} type.
\versionadded{2.3}
\end{datadesc}
\begin{datadesc}{True}
The true value of the \class{bool} type.
\versionadded{2.3}
\end{datadesc}
\begin{datadesc}{None}
The sole value of \code{\refmodule{types}.NoneType}. \code{None} is
frequently used to represent the absence of a value, as when default
arguments are not passed to a function.
\end{datadesc}
\begin{datadesc}{NotImplemented}
Special value which can be returned by the ``rich comparison''
special methods (\method{__eq__()}, \method{__lt__()}, and friends),
to indicate that the comparison is not implemented with respect to
the other type.
\end{datadesc}
\begin{datadesc}{Ellipsis}
Special value used in conjunction with extended slicing syntax.
% XXX Someone who understands extended slicing should fill in here.
\end{datadesc}
