Could you include the rest of the cases that LCatro was mentioning? He mentioned another 2 for lists.

@pablogsal

poc3 is not reproducible on my local mac machine and Linux machine with the master branch.
Looks like the master branch code was changed

However poc2 is reproducible, so I will add the patch on this PR.

$ cat poc3.py
class poc() :
    def __eq__(self,other) :
        list1.clear()
        return NotImplemented

list1 = [ set() ]
poc() in list1
print('end')

$ ./python poc3.py
end

FWIW, LCatro had opened another issue (https://bugs.python.org/issue38610) for similar crashes in the index(), count(), and remove() methods of list. I had created GH-17022 to address them.

@pablogsal
Please take a look,
I 've added the list case patch except which is not reproducible in the master branch.
(I've attached the script above)

And for the list_richcompare I've added more cases that were not reported by LCatro.
Both cases are added in the unit test and fixed.

And IMHO, we can close bpo-38588 with this patch
:)