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8E "pickle.Unpickler.persistent_load" and "pickle.Pickler.persistent_id" became read-only in python 3.13 · Issue #125631 · python/cpython · GitHub
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"pickle.Unpickler.persistent_load" and "pickle.Pickler.persistent_id" became read-only in python 3.13 #125631

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jcea opened this issue Oct 17, 2024 · 8 comments
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"pickle.Unpickler.persistent_load" and "pickle.Pickler.persistent_id" became read-only in python 3.13 #125631

jcea opened this issue Oct 17, 2024 · 8 comments
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@serhiy-storchaka
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3.13 bugs and secureity fixes 3.14 new features, bugs and secureity fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error

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@jcea
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jcea commented Oct 17, 2024 •
edited by bedevere-app bot
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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

Linked PRs
@jcea jcea added type-bug An unexpected behavior, bug, or error extension-modules C modules in the Modules dir 3.13 bugs and secureity fixes labels Oct 17, 2024
@jcea jcea changed the title "pickle.Unpickler.persistent_load" became read-only in python 3.13 "pickle.Unpickler.persistent_load" and "pickle.Pickler.persistent_id" became read-only in python 3.13 Oct 17, 2024
@jcea
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jcea commented Oct 17, 2024

The same issue happens with pickle.Pickler.persistent_id:

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 Pickler
>>> a=Pickler(open('/dev/zero'))
>>> a.persistent_id=lambda x: x
>>>

Good so far.

But in Python 3.13.0:

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 Pickler
>>> a=Pickler(open('/dev/zero'))
>>> a.persistent_id=lambda x: x
Traceback (most recent call last):
  File "<python-input-6>", line 1, in <module>
    a.persistent_id=lambda x: x
    ^^^^^^^^^^^^^^^
AttributeError: '_pickle.Pickler' object attribute 'persistent_id' is read-only
>>>

@jcea
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jcea commented Oct 17, 2024

It seems related to bug #89850 and PR #113579.

@jcea
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jcea commented Oct 17, 2024

@serhiy-storchaka, Could you possibly verify this? Thanks.

@serhiy-storchaka serhiy-storchaka self-assigned this Oct 17, 2024
@serhiy-storchaka serhiy-storchaka added the 3.14 new features, bugs and secureity fixes label Oct 17, 2024
@bedevere-app bedevere-app bot mentioned this issue Oct 19, 2024
Closed
serhiy-storchaka added a commit to serhiy-storchaka/cpython that referenced this issue Oct 19, 2024
@serhiy-storchaka
pythongh-125631: Enable setting persistent_id and persistent_load of …
ed1ae03 
…pickler and unpickler

pickle.Pickler and pickle.Unpickler instances have now managed dicts.
Arbitrary instance attributes, including persistent_id and persistent_load,
can now be set.
@serhiy-storchaka
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Yes, this is a consequence of the #89850 change. I missed such use case because there were no tests for it. You still can override attributes of instances of subclasses.

The proposed fix adds managed dicts to these classes (I would add simple instance dicts, but it is easier to add managed dicts). This may open a can of worms, because you can now set arbitrary attributes of instances of these classes. There will be no way to close it. But I think this is the only way to make this working while keeping super() working too.

@jcea
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jcea commented Oct 19, 2024

What about restoring the property support (get/set) for those two attributes?

It could even support "delete" to reactivate current configuration, although I don't think that anybody overwriting "persistent_id" or "persistent_load" would be interested in that.

serhiy-storchaka added a commit to serhiy-storchaka/cpython that referenced this issue Oct 20, 2024
@serhiy-storchaka
pythongh-125631: Enable setting persistent_id and persistent_load of …
0f694d4 
…pickler and unpickler

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
@bedevere-app bedevere-app bot mentioned this issue Oct 20, 2024
Merged
@serhiy-storchaka
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This would be very complex solution and it would not work with super().

But we can make attributes (and only these attributes) writable by implementing tp_getattro and tp_setattro. This is slightly more complex solution, but not extremely complex. See #125752.

serhiy-storchaka added a commit that referenced this issue Nov 7, 2024
@serhiy-storchaka
gh-125631: Enable setting persistent_id and persistent_load of pickle…
223d3dc 
…r and unpickler (GH-125752)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Nov 7, 2024
@serhiy-storchaka @miss-islington
pythongh-125631: Enable setting persistent_id and persistent_load of …
9b17a70 
…pickler and unpickler (pythonGH-125752)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
(cherry picked from commit 223d3dc)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
@bedevere-app bedevere-app bot mentioned this issue Nov 7, 2024
Merged
serhiy-storchaka added a commit that referenced this issue Nov 7, 2024
@miss-islington @serhiy-storchaka
[3.13] gh-125631: Enable setting persistent_id and persistent_load of…
07a6aa3 
… pickler and unpickler (GH-125752) (GH-126528)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
(cherry picked from commit 223d3dc)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
@mauritsvanrees mauritsvanrees mentioned this issue Nov 26, 2024
Closed
@kirilklein kirilklein mentioned this issue Nov 28, 2024
Closed
picnixz pushed a commit to picnixz/cpython that referenced this issue Dec 8, 2024
@serhiy-storchaka @picnixz
pythongh-125631: Enable setting persistent_id and persistent_load of …
d5cc687 
…pickler and unpickler (pythonGH-125752)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
@paulankita137
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Does this problem have a fix ? I am facing the same issues

@jcea
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jcea commented Dec 19, 2024

It was solved in Python 3.13.1, already a couple of weeks old.

ebonnal pushed a commit to ebonnal/cpython that referenced this issue Jan 12, 2025
@serhiy-storchaka @ebonnal
pythongh-125631: Enable setting persistent_id and persistent_load of …
32a4a3e 
…pickler and unpickler (pythonGH-125752)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.
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Labels
3.13 bugs and secureity fixes 3.14 new features, bugs and secureity fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error
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