[Python-Dev] Pickle implementation questions
"Martin v. Löwis"
martin at v.loewis.de
Fri Jun 30 07:09:19 CEST 2006
Bruce Christensen wrote:
> In developing a cPickle module for IronPython that's as compatible as
> possible with CPython, these questions have come up:
[I wish you were allowed to read the source code of Python]
> - Where are object.__reduce__ and object.__reduce_ex__ defined, and how
> does copy_reg._reduce_ex fit into the picture?
> PEP 307 states that the
> default __reduce__ implementation for new-style classes implemented in
> Python is copy_reg._reduce. However, in Python 2.4.3 dir(copy_reg)
> indicates that it has no _reduce method.
Yes, it calls copy_reg._reduce_ex now (which also expects the protocol
> - When the optional constructor argument is passed to copy_reg.pickle,
> where is it stored and how is it used by pickle?
It's not used anymore. A comment says
# The constructor_ob function is a vestige of safe for unpickling.
# There is no reason for the caller to pass it anymore.
> - What does copy_reg.constructor() do?
It does this:
if not callable(object):
raise TypeError("constructors must be callable")
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