Bug report
Bug description:
In Python releases previous to 3.13, the following code used to work (this idiom is used in Durus and ZODB persistence systems):
Python 3.12.7 (main, Oct 3 2024, 03:21:52) [GCC 10.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from pickle import Unpickler
>>> a=Unpickler(open('/dev/zero'))
>>> a.persistent_load=lambda x: x
>>>
Fine so far.
In Python 3.13, this doesn't work anymore:
Python 3.13.0 (main, Oct 9 2024, 14:54:06) [GCC 10.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from pickle import Unpickler
>>> a=Unpickler(open('/dev/zero'))
>>> a.persistent_load=lambda x: x
Traceback (most recent call last):
File "<python-input-2>", line 1, in <module>
a.persistent_load=lambda x: x
^^^^^^^^^^^^^^^^^
AttributeError: '_pickle.Unpickler' object attribute 'persistent_load' is read-only
I don't know if this is an intended change or a regression.
PS: The subclass approach works:
Python 3.13.0 (main, Oct 9 2024, 14:54:06) [GCC 10.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from pickle import Unpickler
>>> def x(Unpickler):
... def persistent_load(self, x):
... return x
...
>>> b=x(open("/dev/zero"))
>>>
CPython versions tested on:
3.13
Operating systems tested on:
Linux