mirror of https://github.com/jab/bidict.git
24 lines
930 B
PHP
24 lines
930 B
PHP
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.. _inv-avoids-reference-cycles:
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:attr:`.inv <bidict.BidirectionalMapping.inv>` Avoids Reference Cycles
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----------------------------------------------------------------------
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A careful reader might notice the following...
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>>> from bidict import bidict
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>>> fwd = bidict(one=1)
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>>> inv = fwd.inv
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>>> inv.inv is fwd
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True
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...and become concerned that a bidict and its inverse create a reference cycle.
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If this were true, it would mean that the memory for a bidict
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could not be immediately reclaimed when you retained no more references to it,
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but rather would have to wait for gargage collection to be reclaimed.
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However, under the hood bidict uses a :class:`weakref.ref`
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to store the inverse reference in one direction.
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As a result, when you no longer retain any references to a bidict you create,
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you can be sure that its refcount drops to zero,
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and that its memory will therefore be reclaimed immediately.
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