Hi Steven, You're right, declaring `__eq__` for the class we want to compare would solve this issue. However, we have the tradeoff that
- All classes need to implement the `__eq__` method to compare two instances; - Any class implementing the `__eq__` operator is no longer hashable - Developers might not want to leak the `__eq__` function to other developers; I wouldn't want to invade the implementation of my class just for testing. In terms of the "popularity" of this potential feature, from what I understand (and through my own development), there are testing libraries built with this feature. For example, testfixtures.compare <https://testfixtures.readthedocs.io/en/latest/api.html#testfixtures.compare> can compare two objects recursively, and I am using it in my development for this purpose. On Sun, Jul 26, 2020 at 4:56 AM Steven D'Aprano <st...@pearwood.info> wrote: > On Sat, Jul 25, 2020 at 10:15:16PM -0500, Henry Lin wrote: > > Hey all, > > > > What are thoughts about implementing an object-compare function in the > > unittest package? (Compare two objects recursively, attribute by > > attribute.) > > Why not just ask the objects to compare themselves? > > assertEqual(actual, expected) > > will work if actual and expected define a sensible `__eq__` and are the > same type. If they aren't the same type, why not? > > actual = MyObject(spam=1, eggs=2, cheese=3) > expected = DifferentObject(spam=1, eggs=2, cheese=3) > > > > This seems like a common use case in many testing scenarios, > > I've never come across it. Can you give an example where defining an > `__eq__` method won't be the right solution? > > > > > -- > Steven > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/TDLFBURVX4N4JJP4ELIRLKULR775VNOY/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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