On Tue, Aug 31, 2021 at 7:17 AM Nick Parlante <n...@cs.stanford.edu> wrote: >> >> On what basis do you ascertain whether "==" would work correctly? >> Please explain. > > > Hi Chris, I'm just glancing at the line of code, and doing a little thought > experiment to see if it would get the same output if == was used instead. For > a singleton like None or False or the class like "list" .. == will return the > same answer as "is". Look at these lines; > > if mode is None: > if type(items) is list: > > If that code works with "is" it's going to work with == too. People are not > used to seeing == in these cases, but it works: > > >>> x = None > >>> x is None > True > >>> x == None > True > >>> > >>> t = type([1, 2, 3]) > >>> t is list > True > >>> t == list > True > >>> > >>> fn = list.index > >>> fn is list.index > True > >>> fn == list.index > True > > The situations where "is" is truly needed are rather esoteric. >
>>> class X: ... def __eq__(self, other): return True ... >>> x = X() >>> x is None False >>> x == None True >>> type([1, 2, 3]) is x False >>> type([1, 2, 3]) == x True >>> x is list.index False >>> x == list.index True Revisit your assumptions :) ChrisA _______________________________________________ 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/AA6IIC3I2Q7QNI54CMAD2LTYZLTOT57U/ Code of Conduct: http://python.org/psf/codeofconduct/
