[Python-Dev] redefining is

[Barry Warsaw]

On Fri, 2004-03-19 at 17:57, Phillip J. Eby wrote:
> At 05:40 PM 3/19/04 -0500, Andrew Koenig wrote:
> 
> >Nevertheless, I still wish that expressions such as "x is 'foo'" did not
> >silently differ in outcome from one implementation to another.
> 
> The part that drives me nuts about this discussion is that in my view, "x 
> is 'foo'" has the *same* outcome on all implementations.  That is, it's 
> true if x refers to that exact string object.
> 
> The thing that's different from one implementation to the next is whether 
> there's any chance in hell of x being that same 'foo' string.  But to me, 
> that 'foo' string looks like a *newly created* string, so to the naive 
> glance there's no possible way that it could be the same object.  In other 
> words, it looks like a bad expression to use in the first place: one that's 
> guaranteed to be false, except by accident of implementation.
> 
> So, I have trouble understanding how it is that somebody could get to a 
> place where they think that using 'is' for strings and numbers is a good 
> idea in the first place.

Thanks Phillip.  My sentiments exactly.

-Barry