[Python-Dev] Rationale behind lazy map/filter

[Michael Selik]

> I'm not suggesting restarting at the top (I've elsewhere suggested that
> many such methods would be better as an *iterable* that can be restarted
> at the top by calling iter() multiple times, but that's not the same
> thing). I'm suggesting raising an exception other than StopIteration, so
> that this situation can be detected. If you are writing code that tries
> to resume iterating after the iterator has been exhausted, I have to
> ask: why?

The most obvious case for me would be tailing a file. Loop over the lines
in the file, sleep, then do it again. There are many tasks analogous to
that scenario -- anything querying a shared resource.
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