class Sentence: def __init__(self, text): self.text = text def __repr__(self): return f'Sentence({reprlib.repr(self.text)})' def __iter__(self): return (match.group() for match in RE_WORD.finditer(self.text)) The only difference from Example 17-8 is the __iter__ method, which here is not a generator function (it has no yield) but uses a generator expression to build a generator and then returns it. The end result is the same: the caller of __iter__ gets a generator object.
