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gh-128576: feat: Add decorator functools.lru_cache to method tkinter.Misc.winfo_rgb #128577

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gh-128576: feat: Add decorator functools.lru_cache to method tkinter.Misc.winfo_rgb #128577

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cdbc2d5
feat: Add decorator `functools.lru_cache` to method `tkinter.Misc.win…
Xiaokang2022 Jan 6, 2025
7eea471
📜🤖 Added by blurb_it.
blurb-it[bot] Jan 7, 2025
004cd11
style: Improve the changelog
Xiaokang2022 Jan 7, 2025
27136d7
style: Sort the import
Xiaokang2022 Jan 7, 2025
acce9af
feat: Add magic methods `__eq__` and `__hash__` to class `tkinter.Misc`
Xiaokang2022 Jan 7, 2025
da6a174
fix: Fix the magic method `__eq__`
Xiaokang2022 Jan 7, 2025
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11 changes: 11 additions & 0 deletions Lib/tkinter/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@

import collections
import enum
import functools
import sys
import types

Expand Down Expand Up @@ -1314,6 +1315,7 @@ def winfo_reqwidth(self):
return self.tk.getint(
self.tk.call('winfo', 'reqwidth', self._w))

@functools.lru_cache
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@picnixz picnixz Jan 7, 2025

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LRU-cached methods do not play well with functools.lru_cache if __hash__ and __eq__ are not implemented (see https://docs.python.org/3/faq/programming.html#faq-cache-method-calls) because it also caches the instance.

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@Xiaokang2022 Xiaokang2022 Jan 7, 2025 •
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To make the lru_cache approach work when the station_id is mutable, the class needs to define the __eq__() and __hash__() methods so that the cache can detect relevant attribute updates:

The above is quoted from: https://docs.python.org/3.13/faq/programming.html#faq-cache-method-calls

But in reality, no matter how the attribute is updated, the return value of the method winfo_rgb will not change for a particular parameter.

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@picnixz picnixz Jan 7, 2025

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The problem is not the return value. It's how the cache is built. The instance itself is cached by lru_cache. I'm not sure we want to keep them alive. The method will know in advance all the existing instances of Misc that were created and that used this method. This is something we don't want (the cache is a full-fledged dictionary so a reference to those widgets will remain)

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@picnixz picnixz Jan 7, 2025 •
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Now, even if you add those magic methods, the instance will stil be cached. By the way, is it possible to change the color display of the current widget (e.g., directcolor to greyscale) and that this would affect the return value? if so, we cannot cache this method.

I am really not comfortable with caching tk widgets in general. Those objects should be released whenever they can. It would be an overkill to clear the cache when one object has been deleted as well =/

If LRU-caching is possible, instead of storing the instance itself in the cache, we could store the type and the hash of that instance using a class attribute. We could also remove the instance in __del__ so that the hash value can be reused by other objects.

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@Xiaokang2022 Xiaokang2022 Jan 7, 2025

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By the way, is it possible to change the color display of the current widget (e.g., directcolor to greyscale) and that this would affect the return value?

After my testing, this doesn't affect the return value of the method, if my test method is not wrong.

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@Xiaokang2022 Xiaokang2022 Jan 7, 2025

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If the result is the same for any widget, perhaps the method should be a class method instead of an instance method. This may eliminate the need to cache instances.

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@picnixz picnixz Jan 7, 2025

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But is this always the same? according to the docs, this depends on the widget itself so I'm afraid we cannot do this.

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@Xiaokang2022 Xiaokang2022 Jan 7, 2025

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Although the documentation says that, I haven't found a way to corroborate what the documentation says, and if there is a way, hopefully it can be pointed out.

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cc @serhiy-storchaka

def winfo_rgb(self, color):
"""Return a tuple of integer RGB values in range(65536) for color in this widget."""
return self._getints(
Expand Down Expand Up @@ -1848,6 +1850,15 @@ def __repr__(self):
return '<%s.%s object %s>' % (
self.__class__.__module__, self.__class__.__qualname__, self._w)

def __eq__(self, other):
if isinstance(other, Misc):
return self._w == other._w

return False

def __hash__(self):
return hash(self._w)

# Pack methods that apply to the master
_noarg_ = ['_noarg_']

Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-01-07-05-25-57.gh-issue-128576.qzDkju.rst
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@@ -0,0 +1,2 @@
Add decorator :func:`functools.lru_cache` to the :mod:`tkinter` method
:meth:`!winfo_rgb`.
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