On Sun, Apr 22, 2012 at 1:14 PM, Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > The CPython interpreter is especially aggressive in optimizing multiple > literals in the same line. Compare this: > >>>> x = 3.1; y = 3.1; x is y > True > > with this: > >>>> x = 3.1 >>>> y = 3.1 >>>> x is y > False > > > Again, this is an accident of implementation, and cannot be relied on.
That's the interactive interpreter, which works on a basis of lines. With .py files, both 2.6 and 3.2 on Windows appear to do the same optimization at module level. But either way, that's optimization of constants. >>> x=3.1+1.0; y=3.1+1.0; x is y False >>> x=3.1; y=3.1; x+y is x+y False Which can have micro-optimization implications: >>> x=1048576; y=1048576; x is y True >>> x=1<<20; y=1<<20; x is y False But if you're concerning yourself with this kind of optimization, you're probably wasting your time. :) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
