Split string by given separator and return iterator as a result.

The naive and not very efficient solution would be using current str.split:

def split_iter(self: str, sep: str) -> 'Iterator[str]':
    return iter(self.split(sep))

Probably, need we'll some better solution without allocating new list.

I am pretty sure this has been discussed and rejected on the Python-Ideas mailing list before.

If not rejected, the idea didn't go very far. You may wish to search the mailing list archives for previous discussions.

Either way, I think this should be discussed on Python-Ideas, to see if there is a consensus on this, and whether or not this is a large enough change that it needs a PEP.

See also discussion here: #17343

Issue17343 mentions also a separate method str.itersplit, so I close this issue as a duplicate.