efficiency of range() and xrange() in for loops

[Carl Banks]

Steve R. Hastings wrote:
> I wondered if the Python
> compiler could, as a special case, turn:
>
> for i in range(n)
>
> into compiled code equivalent to
>
> for i in itr
>
> where "itr" is a lightweight iterator that returns the same values as
> iter(range(n)).

Nope, out of the question for Python 2.x.  Note that the the builtin
range could be rebound, or a global range could appear in the module,
at run time.  There might even be a good reason to do so....  Point is,
optimizing the call to range can break compatibility even in the for
loop.


Carl Banks