getpixel() should work with list of length 2

[cipri-tom]

What did you do?

img.getpixel([473, 653])

What did you expect to happen?

the pixel at that position is returned

What actually happened?

An unexpected error message: TypeError: argument must be sequence of length 2

But the argument is a sequence of length 2

What are your OS, Python and Pillow versions?

• OS: Ubuntu 18.04
• Python: 3.9
• Pillow: '9.4.0'

img = Image.open('test.png')
img.getpixel([473, 653])

[hugovk]

It's expecting a tuple not a list:

https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.getpixel

Pillow/src/_imaging.c

Lines 1149 to 1151 in 643a52a

	if (!PyTuple_Check(xy) || PyTuple_GET_SIZE(xy) != 2) {
	goto badarg;
	}

Pillow/src/_imaging.c

Lines 1183 to 1185 in 643a52a

	badarg:
	PyErr_SetString(PyExc_TypeError, "argument must be sequence of length 2");
	return -1;

[homm]

It's expecting a tuple not a list:

But the question is why it can't be a list? "argument must be sequence of length 2", list is also a sequence. So behavior or message should be changed.

[cipri-tom]

Exactly! Thanks, @homm

Of course, I would much prefer it it could take any sequence of 2 integers, so we could pass lists, numpy arrays, etc, as long as they have 2 integers.

Would probably have been easier if it took 2 integer arguments, but I suppose there's no changing the interface now

[Yay295]

I think that could be done actually. Something like this:

def getPixel(self, x, y=None):
    if y is None:
        xy = tuple(x)
    else:
        xy = (x, y)

[radarhere]

I've created PR #7355 to allow img.getpixel([473, 653]).

It does not allow im.getpixel(473, 563). In a discussion about trying to clarify things after a confusing error message, it seems to me that "either an argument of sequence of length 2 or two arguments of single integer" is not a step towards clarity. But if someone else would like to create a PR for that change, they are free to do so and see it if receives approval from others.

[cipri-tom]

Thank you for such quick decision and acting !