I don't like consuming the iterator in the exception case. You might expect just one, but have a fallback approach for more. You could build the safer behavior using itertools.tee() or itertools.chain().
On Mon, Jul 27, 2020, 3:10 PM Noam Yorav-Raphael email@example.com wrote:
There's a simple function that I use many times, and I think may be a good fit to be added to itertools. A function that gets an iterator, and if it has exactly one element returns it, and otherwise raises an exception. This is very useful for cases where I do some sort of query that I expect to get exactly one result, and I want an exception to be raised if I'm wrong. For example:
jack = one(p for p in people if p.id == '1234')
sqlalchemy already has such a function for queries: https://docs.sqlalchemy.org/en/13/orm/query.html#sqlalchemy.orm.query.Query....
This is my implementation:
def one(iterable): it = iter(iterable) try: r = next(it) except StopIteration: raise ValueError("Iterator is empty") try: next(it) except StopIteration: return r else: raise ValueError("Iterator has more than one item")
What do you think?
Thanks, Noam _______________________________________________ Python-Dev mailing list -- firstname.lastname@example.org To unsubscribe send an email to email@example.com https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://firstname.lastname@example.org/message/D52MPKLI... Code of Conduct: http://python.org/psf/codeofconduct/