On Thu, 26 Apr 2012 11:31:39 -0700, John Nagle wrote: > I would suggest that "is" raise ValueError for the ambiguous cases. > If both operands are immutable, "is" should raise ValueError. That's the > case where the internal representation of immutables shows through.
This breaks one of the most common uses of "is", i.e. "x is None". And it doesn't prevent a programmer from consfusing "is" and "==" with mutable types. > If this breaks a program, it was broken anyway. It will > catch bad comparisons like > > if x is 1000 : > ... > > which is implementation dependent. The only way to completely eliminate bugs caused by the programmer relying upon implementation-dependent behaviour is to eliminate implementation- dependent behaviour altogether, which is throwing the baby out with the bath water, IMHO. All practical languages have some implementation-defined behaviour, often far more problematic than Python's. -- http://mail.python.org/mailman/listinfo/python-list
