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Implement frozendict for partialobject in functools module #145478
Description
Feature or enhancement
Proposal:
After discussion on PR #145362, it became clear that there are many possibilities for unintended mutations in the partialobject in Module/_functoolsmodule.c, particularly for the kw dictionary for keywords. Thus, changing kw to be a frozendict could prevent any unintended consequences.
Additionally, right now, the keys of kw could be an arbitrary PyObject, leading to unintended code execution if they are not strings. Thus, enforcing that the entries are strings could solve any future problems (similar to what happened in #145362).
Lastly, Issue #145446 also makes sure that there are no unintended mutations in the functools internals for free-threading, but changing to using a frozendict would be a more robust solution.
I will work on this and create a PR in the next couple of days. I will wait until #145446 is resolved to avoid any conflicts.
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Activity
rhettinger commentedon Mar 3, 2026
This sounds like a reasonable approach. Immutable dictionaries can provide early detection or prevention for a number of subtle problems, especially those arising from free-threading.
brijkapadia commentedon Mar 12, 2026
Update: While I was working on this issue, I found that it would be convenient to have a way to convert a
frozendictto adictsince a normal keywords dictionary is needed when calling functions. As such, I am waiting to create a PR until #145531 is merged.vstinner commentedon Mar 12, 2026
Currently, you can use
dict = PyObject_CallOneArg((PyObject*)&PyDict_Type, frozendict);which calls thedictconstructor. In my PR gh-145531, I proposed addingPyAnyDict_AsNewDict()function for that.pythongh-145478: Implement `frozendict` into `functools.partial`