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_BaseDiff evaluates to incorrect boolean

See original GitHub issue

Astropy 4.2.1

Consider the following:

>>> h1 = fits.Header()
>>> if fits.HeaderDiff(h1, h1): print('These are the same')
... 
>>>

Nothing is printed.

The culprit is in _BaseDiff.__bool__: https://github.com/astropy/astropy/blob/e183e398d8bdbbe5c7ccec7a793afed2ecdac4e1/astropy/io/fits/diff.py#L74-L80

Despite the docstring (and other documentation) suggesting that identical objects evaluate to True the return value here is not self.identical.

I tried making a quick fix to this but it broke 19 tests in io.fits so I figured I’d better leave this to the professionals 😃

Issue Analytics

State:
Created 2 years ago
Comments:5 (5 by maintainers)

Top GitHub Comments

2reactions

eigenbrotcommented, Jun 2, 2021

Yep! My plan is to work on this and #11770. Hopefully somewhat soon. If someone wants to assign this issue to me I’m fine with it!

1reaction

pllimcommented, May 21, 2021

Maybe the docstring is wrong. I interpret that when bool(diff) is True, there is a difference, and False when there is no difference (i.e., things are the same). @saimn or @embray , what do you think?

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