The copy_reg defines two functions, _reduce() and
_reconstructor(), that are used for the pickling and
unpickling of new-style classes. These were originally
written in Python because the right implementation
wasn't entirely clear; _reduce() is actually called
from a C-level __reduce__ method defined in 'object',
and it references _reconstructor() in its return tuple.
It is now time to move both back into C for efficiency.

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I'd like to add some comments from Jim Fulton on this (or a
related) issue so they don't get lost.

"""
I still need to think of a good way to handle this. 
Currently, the pattern is a reduce return value of the form:

   reconstructor, (some_class, object, None), some_state

but there is a more general case where an uninitialized
object can be gotten by calling "type.__new__(some_class)",
or even: "some_class.__new__(some_class)".

There are really two issues:

- It's too hard to write __reduce__ functions for this case, and

- Too much data needs to be stored in pickles.

A new pickling code would handler the later, but I also want
to solve the former problem.

One thought is to return: (copy_reg.new, (some_class, ),
some_state) where copy_reg.new is:

   def new(class_): return class.__new__(class_)

The pickler could easily spot reduce returns with
copy_reg.new as the first value and generate a special
pickle code.
"""

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Lowering priority; when you use pickle protocol 2, none of
this Python code is used any more.

Jim's comment has been addressed by __newobj__ and
__getnewargs__ (see PEP 307).

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Except that the new Python code _better_reduce() is used 
then.  As discussed, I intend to rewrite _reduce and 
_better_reduce in C, inside object's __reduce__ 
implementation, so I assigned this to me and boosted the 
priority.  I don't intend to recode _reconstructor in C, 
though.

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This isn't going to be done for 2.3a2; we'll revisit who
gets to do it closer to 2.3b1.

Classifying as an RFE since this is not critical (as shown by it not
happening since early 2003).

I just don't see this happening. Possibly it's out of date. Lots of
things have changed in the pickle world since 2002.