Use ABCMeta in classes with abstractmethod by radarhere · Pull Request #8803 · python-pillow/Pillow

radarhere · Mar 5, 2025

https://docs.python.org/3/library/abc.html#abc.abstractmethod

@abc.abstractmethod
A decorator indicating abstract methods.

Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it.

This is true. In main,

>>> from PIL import Image
>>> Image.ImagePointHandler()
<PIL.Image.ImagePointHandler object at 0x1044f93d0>

but once this PR changes the class to inherit from abc.ABC,

>>> from PIL import Image
>>> Image.ImagePointHandler()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class ImagePointHandler with abstract method point

While I'm here, I'm also going to replace

Pillow/src/PIL/ImageFile.py

Lines 458 to 460 in 7552893

    
           def _open(self) -> None: 
        
               msg = "StubImageFile subclass must implement _open" 
        
               raise NotImplementedError(msg)

and

Pillow/src/PIL/ImageFile.py

Lines 474 to 477 in 7552893

    
           def _load(self) -> StubHandler | None: 
        
               """(Hook) Find actual image loader.""" 
        
               msg = "StubImageFile subclass must implement _load" 
        
               raise NotImplementedError(msg)

with abstract methods.

radarhere added 2 commits March 5, 2025 21:30

Inherit classes with abstractmethod from ABC

2309f0f

Replace NotImplementedError with abstractmethod

d186a2a

radarhere force-pushed the abstract branch from a4bfecd to d186a2a Compare March 5, 2025 10:51

radarhere changed the title ~~Inherit classes with abstractmethod from ABC~~ Use ABCMeta in classes with abstractmethod Mar 5, 2025

hugovk merged commit 5e9eea1 into python-pillow:main Mar 5, 2025

radarhere deleted the abstract branch March 5, 2025 20:46

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Use ABCMeta in classes with abstractmethod#8803

Use ABCMeta in classes with abstractmethod#8803
hugovk merged 2 commits into
python-pillow:mainpython-pillow/Pillow:mainfrom
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radarhere commented Mar 5, 2025 •

edited

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	def _open(self) -> None:
	msg = "StubImageFile subclass must implement _open"
	raise NotImplementedError(msg)

	def _load(self) -> StubHandler \| None:
	"""(Hook) Find actual image loader."""
	msg = "StubImageFile subclass must implement _load"
	raise NotImplementedError(msg)

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radarhere commented Mar 5, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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radarhere commented Mar 5, 2025 •

edited

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