[issue13735] The protocol > 0 of cPickle does not given stable dictionary values

[Antoine Pitrou]

Antoine Pitrou <pitrou at free.fr> added the comment:

I think the "premature" optimization comes down to that code:

"""
static int
put(Picklerobject *self, PyObject *ob)
{
    if (Py_REFCNT(ob) < 2 || self->fast)
        return 0;

    return put2(self, ob);
}
"""

(put2() being the function which emits BINPUT)

When you unpickle a dict, its contents are created anew and therefore the refcount is 1 => next pickling avoids emitting a BINPUT.

----------

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13735>
_______________________________________