如何将其转换为单线发生器？

Question

我最好的尝试失败了：

for s in self.services:
  for m in s.messages: yield m

Answer 1

(m for s in self.services for m in s.messages)

......看起来像反直觉一样。

Answer 2

itertools.chain.from_iterable(s.messages for s in self.services)