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Add __newobj__ and TBD section.

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Guido van Rossum 2003-02-01 20:10:35 +00:00
parent 9cdeaa0b57
commit ccc70922b4
1 changed files with 31 additions and 4 deletions
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pep-0307.txt
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@ -133,10 +133,11 @@ Extended __reduce__ API
in this PEP. The items are, in order:
function A callable object (not necessarily a function) called
to create the initial version of the object; state may
be added to the object later to fully reconstruct the
pickled state. This function must itself be
picklable.
to create the initial version of the object; state
may be added to the object later to fully reconstruct
the pickled state. This function must itself be
picklable. See the section about __newobj__ for a
special case (new in this PEP) here.
arguments A tuple giving the argument list for the function.
As a special case, designed for Zope 2's
@ -184,6 +185,32 @@ Extended __reduce__ API
state with value None.
The __newobj__ unpickling function
When the unpickling function returned by __reduce__ (the first
item of the returned tuple) has the name __newobj__, something
special happens for pickle protocol 2. An unpickling function
named __newobj__ is assumed to have the following semantics:
def __newobj__(cls, *args):
return cls.__new__(cls, *args)
Pickle protocol 2 special-cases an unpickling function with this
name, and emits a pickling opcode that, given 'cls' and 'args',
will return cls.__new__(cls, *args) without also pickling a
reference to __newobj__. This is the main reason why protocol 2
pickles are so much smaller than classic pickles. Of course, the
pickling code cannot verify that a function named __newobj__
actually has the expected semantics. If you use an unpickling
function named __newobj__ that returns something different, you
deserve what you get.
TBD
The rest of this PEP is still under construction!
Copyright
This document has been placed in the public domain.