Interesting. Did you look at the code? It is here (that's the `==` operator you're complaining about):

https://github.com/python/cpython/blob/6afb730e2a8bf0b472b4c3157bcf5b44aa7e6d56/Lib/unittest/case.py#L970

The code does already analyze the length of the sequence

You are right that collections.abc.Sequence (or its ancestors other than object) does not implement `__eq__`, so it would seem that the `==` operator would have to be replaced with a simple loop:
```
for x, y in zip(seq1, seq2):
if x is not y and x != y:
break
else:
return  # They are all equal
```
Making that change would probably slow things down. (Note that the odd check "x is not y and x != y" is needed to keep the previous behavior regarding NaN and other objects that aren't equal to themselves.)

```
For the purposes of this function, a valid ordered sequence type is one
which can be indexed, has a length, and has an equality operator.
```
IOW, I think this ship has actually sailed.

On Tue, Dec 22, 2020 at 10:56 AM Alan G. Isaac <alan.isaac@gmail.com> wrote:
The following test fails because because `seq1 == seq2` returns a (boolean) NumPy array
whenever either seq is a NumPy array.

import unittest
import numpy as np
unittest.TestCase().assertSequenceEqual([1.,2.,3.], np.array([1.,2.,3.]))

I expected `unittest` to rely only on features of a `collections.abc.Sequence`,
which based on https://docs.python.org/3/glossary.html#term-sequence,
I believe are satisfied by a NumPy array. Specifically, I see no requirement
that a sequence implement __eq__ at all much less in any particular way.

In short: a test named `assertSequenceEqual` should, I would think,
work for any sequence and therefore (based on the available documentation)
should not depend on the class-specific implementation of __eq__.

Is that wrong?

Thank you, Alan Isaac
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-leave@python.org
https://mail.python.org/mailman3/lists/python-dev.python.org/
Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/6Z43SU2RPIHTRABYAXBOGRKWGTLIFJYK/
Code of Conduct: http://python.org/psf/codeofconduct/

--
--Guido van Rossum (python.org/~guido)
Pronouns: he/him (why is my pronoun here?)