Special Types
=============



.. toctree::
   :maxdepth: 1


Indices and tables
------------------

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`


Definition
----------
Python defines several types which don't fit neatly in the other categories. They are covered here.


.. _section_heading-None:

None
----
A built-in "null" like object that is used to represent something that is unknown, non-existent or has an absence of value.
Its truth value is False.

    >>> bool(None)
    False

There is only one object with this value.

.. tip:: Testing a value against None is fast when done using the :keyword:`is` function, since it tests for identity, which is fast in Python.


.. _section_heading-NotImplemented:

NotImplemented
--------------
A build-in object used to signify that a function or method, although defined, is not implemented.
Its truth value is True.

    >>> bool(NotImplemented)
    True

There is ony one object with this value.


.. _section_heading-Elipses:

Elipses
-------
A built-in object used in slicing notation. It was created mainly for working with the Python numeric extensions NumPy and SciPy. It will not be covered further in this course.