On Wed, Dec 4, 2019 at 16:33 Juancarlo Añez <juancarlo.anez@gmail.com> wrote: is troublesome.
The proposed implementation of a findfirst() would handle many common cases, and be friendly to newcomers (why do I need to deal with a Match object?), specially if the semantics are those of findall():
next(iter(findall(...)), default=default)
BTW, a common function in extensions to itertools is first():
def first(seq, default=None): return next(iter(seq), default= default)
That function, first(), would also be a nice addition in itertools, and findfirst() could be implemented using it. first() avoids most use cases needing to check if a sequence or iterator is empty before using a default value. MHO is that first() deals with so many common cases that it should be a builtin.
I agree that there should be a builtin like first but to be clear it should not raise StopIteration if the iterator turns out to be empty. Probably it should raise ValueError analogous to
a, *_ = [] Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: not enough values to unpack (expected at least 1, got 0)
-- Oscar