On Thu, Apr 26, 2012 at 5:39 PM, Ian Kelly <ian.g.ke...@gmail.com> wrote: > On Thu, Apr 26, 2012 at 1:34 PM, Adam Skutt <ask...@gmail.com> wrote: >> What I think you want is what I said above: ValueError raised when >> either operand is a /temporary/ object. Really, it should probably be >> a parse-time error, since you could (and should) make the >> determination at parse time. > > I'm not sure precisely what you mean by "temporary object", so I am > taking it to mean an object that is referenced only by the VM stack > (or something equivalent for other implementations). > > In that case: no, you can't. Take "f() is g()", where the code > objects of f and g are supplied at runtime. Are the objects returned > by either of those expressions "temporary"? Without being able to do > static analysis of the code of f and g, there is no way to know.
A temporary object would be anything that need not be alive longer than the duration of the 'is' operation. I am not a Python language expert so that definition may not be exactly correct or workable for Python. In the example: >>> [1, 2] is [3, 4] [1,2] and [3,4] don't need to exist before the 'is' operation, nor after it, so they are temporaries. Adam -- http://mail.python.org/mailman/listinfo/python-list
