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GH-103475: cache() and lru_cache() do not have a "call once" guarantee (GH-103669)

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Raymond Hettinger 2023-04-22 09:18:25 -05:00 committed by GitHub
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Doc/library/functools.rst
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@ -49,8 +49,13 @@ The :mod:`functools` module defines the following functions:
>>> factorial(12) # makes two new recursive calls, the other 10 are cached >>> factorial(12) # makes two new recursive calls, the other 10 are cached
479001600 479001600
The cache is threadsafe so the wrapped function can be used in multiple The cache is threadsafe so that the wrapped function can be used in
threads. multiple threads. This means that the underlying data structure will
remain coherent during concurrent updates.
It is possible for the wrapped function to be called more than once if
another thread makes an additional call before the initial call has been
completed and cached.
.. versionadded:: 3.9 .. versionadded:: 3.9
@ -158,8 +163,13 @@ The :mod:`functools` module defines the following functions:
*maxsize* most recent calls. It can save time when an expensive or I/O bound *maxsize* most recent calls. It can save time when an expensive or I/O bound
function is periodically called with the same arguments. function is periodically called with the same arguments.
The cache is threadsafe so the wrapped function can be used in multiple The cache is threadsafe so that the wrapped function can be used in
threads. multiple threads. This means that the underlying data structure will
remain coherent during concurrent updates.
It is possible for the wrapped function to be called more than once if
another thread makes an additional call before the initial call has been
completed and cached.
Since a dictionary is used to cache results, the positional and keyword Since a dictionary is used to cache results, the positional and keyword
arguments to the function must be :term:`hashable`. arguments to the function must be :term:`hashable`.