["python","iterator","generator"]
Why is there no first(iterable) built-in function in Python?

I'm wondering if there's a reason that there's no first(iterable) in the Python built-in functions, somewhat similar to any(iterable) and all(iterable) (it may be tucked in a stdlib module somewhere, but I don't see it in itertools). first would perform a short-circuit generator evaluation so that unnecessary (and a potentially infinite number of) operations can be avoided; i.e. def identity(item): return item def first(iterable, predicate=identity): for item in iterable: if predicate(item): return item raise ValueError('No satisfactory value found') This way you can express things like: denominators = (2, 3, 4, 5) lcd = first(i for i in itertools.count(1) if all(i % denominators == 0 for denominator in denominators)) Clearly you can't do list(generator)[0] in that case, since the generator doesn't terminate. Or if you have a bunch of regexes to match against (useful when they all have the same groupdict interface): match = first(regex.match(big_text) for regex in regexes) You save a lot of unnecessary processing by avoiding list(generator)[0] and short-circuiting on a positive match.
In Python 2, if you have an iterator, you can just call its next method. Something like: >>> (5*x for x in xrange(2,4)).next() 10 In Python 3, you can use the next built-in with an iterator: >>> next(5*x for x in range(2,4)) 10