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explain why hash is not the default

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Benjamin Peterson 2017-09-07 15:36:48 -07:00
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pep-0552.txt
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@ -46,7 +46,13 @@ Distributors of Python code are currently stuck with the options of
4. doing a complicated mixture of 1. and 2. like generating pycs at installation 4. doing a complicated mixture of 1. and 2. like generating pycs at installation
time time
None of these options are very attractive. This PEP proposes a better solution. None of these options are very attractive. This PEP proposes allowing the
timestamp to be replaced with a deterministic hash. The current timestamp
invalidation method will remain the default, though. Despite its nondeterminism,
timestamp invalidation works well for many workflows and usecases. The
hash-based pyc format can impose the cost of reading and hashing every source
file, which is more expensive than simply checking timestamps. Thus, for now, we
expect it to be used mainly by distributors and power use cases.
(Note there are other problems [#frozensets]_ [#interning]_ we do not (Note there are other problems [#frozensets]_ [#interning]_ we do not
address here that can make pycs non-deterministic.) address here that can make pycs non-deterministic.)