4 A small number of constants live in the built-in namespace. They are:
9 The false value of the :class:`bool` type.
16 The true value of the :class:`bool` type.
23 The sole value of :attr:`types.NoneType`. ``None`` is frequently used to
24 represent the absence of a value, as when default arguments are not passed to a
27 .. versionchanged:: 2.4
28 Assignments to ``None`` are illegal and raise a :exc:`SyntaxError`.
31 .. data:: NotImplemented
33 Special value which can be returned by the "rich comparison" special methods
34 (:meth:`__eq__`, :meth:`__lt__`, and friends), to indicate that the comparison
35 is not implemented with respect to the other type.
40 Special value used in conjunction with extended slicing syntax.
42 .. XXX Someone who understands extended slicing should fill in here.
47 This constant is true if Python was not started with an :option:`-O` option.
48 Assignments to :const:`__debug__` are illegal and raise a :exc:`SyntaxError`.
49 See also the :keyword:`assert` statement.
52 Constants added by the :mod:`site` module
53 -----------------------------------------
55 The :mod:`site` module (which is imported automatically during startup, except
56 if the :option:`-S` command-line option is given) adds several constants to the
57 built-in namespace. They are useful for the interactive interpreter shell and
58 should not be used in programs.
60 .. data:: quit([code=None])
63 Objects that when printed, print a message like "Use quit() or Ctrl-D
64 (i.e. EOF) to exit", and when called, raise :exc:`SystemExit` with the
65 specified exit code, and when .
71 Objects that when printed, print a message like "Type license() to see the
72 full license text", and when called, display the corresponding text in a
73 pager-like fashion (one screen at a time).