.. _inv-avoids-reference-cycles:

:attr:`.inv <bidict.BidirectionalMapping.inv>` Avoids Reference Cycles
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A careful reader might notice the following...

    >>> from bidict import bidict
    >>> fwd = bidict(one=1)
    >>> inv = fwd.inv
    >>> inv.inv is fwd
    True

...and become concerned that a bidict and its inverse create a reference cycle.
If this were true, it would mean that the memory for a bidict
could not be immediately reclaimed when you retained no more references to it,
but rather would have to wait for gargage collection to be reclaimed.

However, under the hood bidict uses a :class:`weakref.ref`
to store the inverse reference in one direction.
As a result, when you no longer retain any references to a bidict you create,
you can be sure that its refcount drops to zero,
and that its memory will therefore be reclaimed immediately.