Paul Ganssle <[email protected]> added the comment:
Serhiy: I think at least a test for this particular corner case should be
added, so that no implementations of `isinstance` that use the CPython test
suite hit an infinite recursion in that event, I guess?
Though I think it's maybe an open question as to what the correct behavior is.
Should we throw on any tuple subclass because there's no reason to support
tuple subclasses? Should we switch to using __iter__ when it's defined because
there are other cases where the custom behavior of the subclass is defined by
its __iter__? Should we make it a guarantee that __iter__ is *never* called?
I can't really think of a reason why defining __iter__ on a tuple subclass
would be anything other than a weird hack, so I would probably say either ban
tuple subclasses or add a test like so:
def testIsinstanceIterNeverCalled(self):
"""Guarantee that __iter__ is never called when isinstance is invoked"""
class NoIterTuple(tuple):
def __iter__(self): # pragma: nocover
raise NotImplemented("Cannot call __iter__ on this.")
self.assertTrue(isinstance(1, NoIterTuple((int,))))
----------
nosy: +p-ganssle
_______________________________________
Python tracker <[email protected]>
<https://bugs.python.org/issue39550>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
