This is not just about the content of the name attributes: ;bound methods do contain a reference to the specific instance they are bound too - which is not retrievable (or maybe is through some dunder attribute) - this instance has to be pickled, transported and its reference updated on unpickling.
On Fri, Jun 10, 2022 at 9:00 AM haael <ha...@interia.pl> wrote: > > > During some sophisticated pickling I noticed that method `__func__` > objects are unpicklable, because they share the name with the bound > method object itself. > > > ``` > from pickle import dumps > > class A: > @classmethod > def b(cls): > pass > > print(A.b) # <bound method A.b of <class '__main__.A'>> > print(A.b.__func__) # <function A.b at 0x7f5574570bf8> > > dumps(A.b) # works > dumps(A.b.__func__) # breaks > # >Traceback (most recent call last): > # > File "<stdin>", line 1, in <module> > # >_pickle.PicklingError: Can't pickle <function A.b at 0x7fd1d50d8bf8>: > # >it's not the same object as __main__.A.b > ``` > > > The last call compains that global symbol "A.b" is not the same object > as `A.b.__func__`. > > Everything would work if the `__func__` objects had the suffix > ".__func__" in their qualname. > > Actually setting the qualname of the `__func__` object makes it > picklable, but then the bound method object is unpicklable, as it > inherits the name from the `__func__`. It would be good if they were > separate. > > This is an attempt at emulating the desired behavior: > > > ``` > from pickle import dumps > > class A: > pass > > def c(cls): > pass > > A.c = lambda: c(A) > A.c.__qualname__ = "A.c" > A.c.__name__ = "c" > A.c.__self__ = A > A.c.__func__ = c > A.c.__func__.__qualname__ = "A.c.__func__" > > print(A.c) # <function A.c at 0x7f83ceabcbf8> > print(A.c.__func__) # <function A.c.__func__ at 0x7f83ceabcb70> > > dumps(A.c) # works > dumps(A.c.__func__) # works > ``` > > > Can we make the `__func__` objects picklable this way? > > > haael > > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/N2J6MVLURTBAB5PJLJG3LO6U4PTPJMU2/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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