[Python-Dev] Slices and "==" optimization

[Guido van Rossum]

> As with all micro-optimizations, the win usually only shows
> up in some applications. The one I'm writing uses lot's of
> 
> 	if tagtype == 'starttag':
> 	if tagtype == 'endtag':
> 	...
> 
> Since the 'starttag' and 'endtag' strings are interned and
> I'm also interning the strings which are stored in tagtype,
> I'd like to benefit from the fact that the compare will actually
> work as 'is'-compare. However, I don't want to use 'is' because
> I consider interning only an optimization and not a feature
> of the language.

Agreed.

> That's why I would like the simple
> 
> 	if (v == w) return 0;
> 
> integrated into the ceval loop right along the INT-compare
> optimization. 

Maybe this could be done as follows:

    if (v == w && PyString_CheckExact(v)) return 0;

> This may also help in some other situations where objects are
> shared.

Now *that* is the speculation for which Tim will chop off your
head. :-)

--Guido van Rossum (home page: http://www.python.org/~guido/)