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Added type hints to Image.__init__() #8279

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merged 4 commits into from
Aug 28, 2024

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radarhere
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Alternative to #8275

Once the None return type is added to Image.__init__(), a variety of other changes are needed.

Pillow/src/PIL/Image.py

Lines 535 to 544 in d8447de

def __init__(self):
# FIXME: take "new" parameters / other image?
# FIXME: turn mode and size into delegating properties?
self.im = None
self._mode = ""
self._size = (0, 0)
self.palette = None
self.info = {}
self.readonly = 0
self._exif = None

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mergify bot commented Aug 2, 2024

⚠️ The sha of the head commit of this PR conflicts with #7461. Mergify cannot evaluate rules on this PR. ⚠️

@akx
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akx commented Aug 6, 2024

I'm a tiny bit worried about the cost of these assertions within the core library. I think practically no one* runs Python with -O/PYTHONOPTIMIZE that'd wipe these out.

*: entirely anecdotal

@hugovk
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hugovk commented Aug 6, 2024

Some discussion on PYTHONOPTIMIZE, showing it does get used:

https://discuss.python.org/t/does-anyone-use-o-or-oo-or-pythonoptimize-1-in-their-deployments/37671

Please could you run some benchmarks to evaluate the cost?

@radarhere
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There's a variety of changes here, but running

python3.9 -m timeit -r 100 -c 'from PIL import Image;Image.new("L", (1, 1)).copy()'

without this change, I get

100000 loops, best of 100: 2.36 usec per loop

With this change, I get

100000 loops, best of 100: 2.37 usec per loop

@hugovk
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hugovk commented Aug 7, 2024

I think that's close enough not to worry about. There's some variation as well. Running twice:

without this change, I get:

100000 loops, best of 100: 2.45 usec per loop
100000 loops, best of 100: 2.37 usec per loop

with this change, I get:

100000 loops, best of 100: 2.39 usec per loop
100000 loops, best of 100: 2.41 usec per loop

And similar results across 3.12.

Without:

200000 loops, best of 100: 1.49 usec per loop

With:

200000 loops, best of 100: 1.48 usec per loop

@akx Any further concerns?

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akx commented Aug 7, 2024

Now that I think of it, can self.im actually ever practically be None?

Would all of this be simpler if we went for practicality and not purity, and said

self.im: core.ImagingCore = None  # type: ignore[assignment]

or alternatively left self.im unassigned in __init__ and just did

im: core.ImagingCore

as an annotation?

I think #7461 is related here.

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There are other places where it is set to None

self.im = None

self.im = None

self.im = None

The current code does also check that it isn't None

if self.im is not None and self.palette and self.palette.dirty:

if self.im is not None:

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akx commented Aug 7, 2024

If it's only about 5 places, would it make sense to consider whether those places need to do that?

They could delattr(self, "im") and hasattr(self, "im") instead, maybe?

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Now that I think of it, can self.im actually ever practically be None?

I think #7461 is related here.

This isn't just about the edge case of calling Image.Image() directly. It is None before an image is loaded.

>>> from PIL import Image
>>> im = Image.open("Tests/images/hopper.png")
>>> im.im is None
True
>>> im.load()
<PixelAccess object at 0x105d86510>
>>> im.im is None
False

They could delattr(self, "im") and hasattr(self, "im") instead, maybe?

If code simplicity is the concern rather than speed, how about this idea as a slightly smaller change? I've pushed a commit so that using @property, im.im always returns core.ImagingCore. im._im can be used to check for None.

Comment on lines +546 to +551
@property
def im(self) -> core.ImagingCore:
if isinstance(self._im, DeferredError):
raise self._im.ex
assert self._im is not None
return self._im
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Couldn't self._im still be None here?

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If it is, the assert will stop the code before the return statement is reached.

@hugovk hugovk merged commit 1bf9fb4 into python-pillow:main Aug 28, 2024
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@radarhere radarhere deleted the type_hint_init branch August 28, 2024 07:08
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4 participants