On Fri, Sep 8, 2017 at 1:01 PM, Rustom Mody <rustompm...@gmail.com> wrote: > >> Can you show an actual false positive (two distinct objects for which `is` >> returns True) or false negative (the same object given as both operands for >> `is` nevertheless returns False)? In the absence of any actual bugs in the >> definition, I maintain that it is sufficient. > > You are not paying attention — the example above I gave in which > python arbitrarily hi-handedly, inconsistently manifests different behavior > between integer 1 and tuple (1,2)
You started with the assumption that the tuple (1,2) is the same as the tuple (1,2). This is a false assumption; they are equal, but they are not identical. How does your mathematical model cope with this? >>> x = 1 >>> y = 1.0 >>> x == y True >>> x is y False There is no way that a compliant Python implementation can give any other results for these expressions. These values are equal but not identical. It's the same with the integers and tuples in your example, except that there, Python is permitted to optimize by using the same object. Stop thinking about mathematics and assuming that (a) it is the perfect way to explain software, and (b) we all have the same basis you do. Start thinking about programming languages from a different basis... you might actually learn something. Or just read what Steve and I have been saying. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
