[Guido]
The argument that first(it) and next(it) "look the same" doesn't convince me;
I'm sorry - I guess then I have absolutely no idea what you were trying to say, and read it completely wrong.
if these look the same then all function applications look the same, and that can certainly not have been Meertens' intention.
No argument on that from me ;-)
But if everyone thinks that first() should raise, fine, this thread is way too long already (I should have kept it muted :-).
It was being discussed. The 1-argument more-itertools `first()` does raise on an exhausted iterator, and that does make most sense to me. In my algorithms I usually "know" I'm not trying to take an element from an empty iterable, and have no use for a default value in such a case. Since there's no non-destructive way to assert that the iterable is not exhausted, raising an exception if it is exhausted is most useful. _empty = object() a = first(iterable, _empty) if a is _empty: raise ... is a PITA by comparison, as is my _current_ idiom: for a in iterable: break else: raise ... Plain old a = first(iterable) would be perfect - but only if it raised.