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Concealment
===============================================================================

The ``accretive.concealment`` subpackage offers variants on the main package
modules. These variants conceal all non-public attributes from the
:py:func:`dir` function by default. Normally hidden attributes can be exposed
on instances by providing a class attribute, named
``_attribute_visibility_includes_``. A similar
``_class_attribute_visibility_includes_`` attribute can be provided on
metaclasses to conceal class attributes.

.. doctest:: Concealment

    >>> from accretive.concealment import Object
    >>> class MyObject( Object ):
    ...     _attribute_visibility_includes_ = frozenset( ( '__dunder_attr__', ) )
    ...     def __init__( self ):
    ...         super( ).__init__( )
    ...         self.visible = 'hi'
    ...         self._hidden = '*lurks*'
    ...         self.__dunder_attr__ = 'hi!'
    ...
    >>> obj = MyObject( )
    >>> dir( obj )
    ['__dunder_attr__', 'visible']
    >>> obj._hidden
    '*lurks*'
    >>> obj.__dict__
    {'visible': 'hi', '_hidden': '*lurks*', '__dunder_attr__': 'hi!'}