[Python-Dev] Accepting PEP 3154 for 3.4?

Tim Peters tim.peters at gmail.com
Tue Nov 19 23:06:22 CET 2013

>>> Ahah, ok, I see where you're going. But how many other implementations
>>> of unpickling are there?

>> That's something you should have researched when writing the PEP ;-)
>> How many implementations of Python aren't CPython?  That's probably
>> the answer.  I'm not an expert on that, but there's more than one.

> But "how many of them use something else than Lib/pickle.py" is the
> actual question.

I don't know - and neither do you ;-)

I do know that I'd like, e.g., a version of pickletools.dis() in
CPython that _did_ show the framing bits, for debugging.  That's a
bare-bones "unpickler".  I don't know how many other "partial
unpicklers" exist in the wild either.  But their lives would also be
much easier if the framing stuff were explicit.  "Mandatory
optimization" should be an oxymoron ;-)

> ...
> The problem with "let's make the unpickler more lenient in a later
> version" is that then you have protocol 4 pickles that won't work with
> all protocol 4-accepting versions of the pickle module.

Yup.  s/4/5/ would need to be part of a delayed optimization.

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