FIX: Handle AxesWidget cleanup after failed init #30935
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QuLogic
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Jan 6, 2026
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timhoffm
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Jan 7, 2026
timhoffm
reviewed
Jan 8, 2026
Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
timhoffm
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Jan 8, 2026
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Maybe instead of defining diff --git i/lib/matplotlib/widgets.py w/lib/matplotlib/widgets.py
index 5e87abe08d..9418794dcf 100644
--- i/lib/matplotlib/widgets.py
+++ w/lib/matplotlib/widgets.py
@@ -120,16 +120,6 @@ class AxesWidget(Widget):
self._cids = []
self._blit_background_id = None
- def __del__(self):
- blit_background_id = getattr(self, '_blit_background_id', None)
- # __del__ may be called on a partially initialized object, e.g.,
- # when __init__ raises. Therefore, we handle missing attributes
- # gracefully.
- if blit_background_id is not None:
- canvas = getattr(self, 'canvas', None)
- if canvas is not None:
- canvas._release_blit_background_id(blit_background_id)
-
canvas = property(
lambda self: getattr(self.ax.get_figure(root=True), 'canvas', None)
)
@@ -170,7 +160,10 @@ class AxesWidget(Widget):
good enough for all existing widgets.
"""
if self._blit_background_id is None:
- self._blit_background_id = self.canvas._get_blit_background_id()
+ bbid = self.canvas._get_blit_background_id()
+ import weakref
+ weakref.finalize(self, self.canvas._release_blit_background_id, bbid)
+ self._blit_background_id = bbid
self.canvas._blit_backgrounds[self._blit_background_id] = background
def _load_blit_background(self):? |
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PR summary
In 3.11.0.dev,
AxesWidget.__del__is called on partially constructed selectors when__init__raises early (e.g.,EllipseSelector(ax, foo="bar")with an invalid kwarg). Because__init__never runs, attributes like_blit_background_idandcanvasare not set, so__del__givesException ignored while calling deallocator <function AxesWidget.__del__ at 0x108598b40>:and raises anAttributeErrorduring garbage collection. This surfaces asPytestUnraisableExceptionWarningin tests in downstream packages.See, e.g., https://github.com/astropy/regions/actions/runs/20730257507/job/59516157314
This bug was introduced in #30591.
Minimal example (also added as a regression test):
PR checklist