[Python-Dev] Short-circuiting iterators (original) (raw)

Raymond Hettinger raymond.hettinger at verizon.net
Thu Dec 8 05:15:55 CET 2005

[Matthew F. Barnes]

The ability to remotely terminate a for-loop also struck me as somewhat interesting:

def estimate(item, iterable): . . . if goodenough: iterable.stop() return result for x in iterable: . . . approx *= estimate(x, iterable)

Good inspiration; wrong technique. For the RightWay(tm), try a functional approach composing a target calculation with a function generating successively more accurate approximations and a consumer function that stops when the desired accuracy is achieved. The idea is to decouple the steps into side-effect-free, reusable components. For a worked-out, comprehensive example, see http://www.md.chalmers.se/~rjmh/Papers/whyfp.pdf .

But these are highly contrived and hardly compelling.

That suggests an answer to your earlier question as to whether itertools.interruptable(iterable) would be a useful addition ;-)

Raymond

More information about the Python-Dev mailing list