[Python-Dev] PEP 552: deterministic pycs

Benjamin Peterson benjamin at python.org
Thu Sep 7 21:54:54 EDT 2017

On Thu, Sep 7, 2017, at 16:58, Gregory P. Smith wrote:
> +1 on this PEP.


> Questions:
> Input from OS package distributors would be interesting.  Would they use
> this?  Which way would it impact their startup time (loading the .py file
> vs just statting it.  does that even matter?  source files are often
> eventually loaded for linecache use in tracebacks anyways)?

I an anticipate distributors will use the mode where the pyc is simply
trusted and the source file isn't hashed. That would make the io
overhead identical to today.

> Would they benefit from a pyc that can contain _both_ timestamp+length,
> and
> the source_hash?  if both were present, I assume that only one would be
> checked at startup.  i'm not sure what would make the decision of what to
> check.  one fails, check the other?  i personally do not have a use for
> this case so i'd omit the complexity without a demonstrated need.

Yeah, it could act as a multi-tiered cache key. I agree with your
conclusion to pass for now.

> Something to also state in the PEP:
> This is intentionally not a "secure" hash.  Security is explicitly a
> non-goal.

Added a sentence.

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