=============
General Utils
=============

.. module:: djem

``UNDEFINED``
=============

.. py:data:: UNDEFINED

    .. versionadded:: 0.7

    The ``UNDEFINED`` constant is a falsey value designed for use in argument default values, for situations in which *any* value given (including traditional argument default values such as ``None``) have an explicit meaning.

    .. code-block:: python

        from djem import UNDEFINED

        def make_thing(name, label=UNDEFINED):

            # None, the empty string, or False could indicate "no label" and need
            # to be distinguished from no value being provided
            if label is UNDEFINED:
                label = name

            ...

    It can also be used in more generic conditional statements:

    .. code-block:: python

        from djem import UNDEFINED

        value = UNDEFINED

        if value:
            print('truthy')
        else:
            print('falsey')

        # output: 'falsey'