5 A small number of constants live in the built-in namespace. They are:
10 The false value of the :class:`bool` type.
17 The true value of the :class:`bool` type.
24 The sole value of :attr:`types.NoneType`. ``None`` is frequently used to
25 represent the absence of a value, as when default arguments are not passed to a
28 .. versionchanged:: 2.4
29 Assignments to ``None`` are illegal and raise a :exc:`SyntaxError`.
32 .. data:: NotImplemented
34 Special value which can be returned by the "rich comparison" special methods
35 (:meth:`__eq__`, :meth:`__lt__`, and friends), to indicate that the comparison
36 is not implemented with respect to the other type.
41 Special value used in conjunction with extended slicing syntax.
43 .. XXX Someone who understands extended slicing should fill in here.
48 This constant is true if Python was not started with an :option:`-O` option.
49 Assignments to :const:`__debug__` are illegal and raise a :exc:`SyntaxError`.
50 See also the :keyword:`assert` statement.