[Python-Dev] Pickling buffer objects.
oliphant at ee.byu.edu
Tue Apr 19 02:47:31 CEST 2005
Before submitting a patch to pickle.py and cPickle.c, I'd be interested
in knowing how likely to be accepted a patch that allows Python to
pickle the buffer object.
The problem being solved is that Numeric currently has to copy all of
its data into a string before writing it out to a pickle. Yes, I know
there are ways to write directly to a file. But, it is desireable to
have Numeric arrays interact seamlessly with other pickleable types
without a separate stream. This is especially utilized for network
The patch would simply write the opcode for a Python string to the
stream and then write the character-interpreted data (without making an
intermediate copy) of the void * pointer of the buffer object.
Yes, I know all of the old arguments about the buffer object and that it
should be replaced with something better. I've read all the old posts
and am quite familiar with the issues about it.
But, this can be considered a separate issue. Since the buffer object
exists, it ought to be pickleable, and it would make a lot of
applications a lot faster.
I'm proposing to pickle the buffer object so that it unpickles as a
string. Arguably, there should be a separate mutable-byte object opcode
so that buffer objects unpickle as mutable-byte buffer objects. If
that is more desireable, I'd even offer a patch to do that (though such
pickles wouldn't unpickle under earlier versions of Python). I suspect
that the buffer object would need to be reworked into something more
along the lines of the previously-proposed bytes object before a
separate bytecode for pickleable mutable-bytes is accepted, however.
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