Method __func__ objects are unpicklable
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
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 <haael@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
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I believe a lot of people use https://pypi.org/project/cloudpickle/ thanks to its support for pickling functions. On Fri, Jun 10, 2022 at 4:56 AM haael <haael@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
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participants (3)
-
Brett Cannon -
haael -
Joao S. O. Bueno