[Python-Dev] marshal (was:Buffer interface in abstract.c? )

[Jack Jansen]

Recently, "Fredrik Lundh" <fredrik@pythonware.com> said:
> on the other hand, I think something is missing from
> the buffer design; I definitely don't like that people
> can write and marshal objects that happen to
> implement the buffer interface, only to find that
> Python didn't do what they expected...
> 
> >>> import unicode
> >>> import marshal
> >>> u = unicode.unicode
> >>> s = u("foo")
> >>> data = marshal.dumps(s)
> >>> marshal.loads(data)
> 'f\000o\000o\000'
> >>> type(marshal.loads(data))
> <type 'string'>

Hmm. Looking at the code there is a catchall at the end, with a
comment explicitly saying "Write unknown buffer-style objects as a string".
IMHO this is an incorrect design, but that's a bit philosophical (so
I'll gladly defer to Our Great Philosopher if he has anything to say
on the matter:-). Unless, of course, there are buffer-style non-string 
objects around that are better read back as strings than not read back 
at all.

Hmm again, I think I'd like it better if marshal.dumps() would barf on 
attempts to write unrepresentable data. Currently unrepresentable
objects are written as TYPE_UNKNOWN (unless they have bufferness (or
should I call that "a buffer-aspect"? :-)), which means you think you
are writing correctly marshalled data but you'll be in for an
exception when you try to read it back...
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