[Barry Warsaw]
> Thanks! I thought it was cute. It was just something that occurred to me
> as I was reviewing some existing code. The intent wasn’t to use `subdirs`
> outside of the assert statement, but I’m warm to it because it means I
> don’t have to do wasted work outside of the assert statement, or repeat
> myself in the assert message part.
>
Because the latter ("repeat myself") is probably more tempting, I'll just
note that the "laziness" of using an assignment expression instead may well
have nudged you toward writing _better_ code too.
assert len(subdirs := list(path.iterdir())) == 0, subdirs
Assuming the result of list(path.iterdir()) can change over time (seems
very likely),
assert len(list(path.iterdir())) == 0, list(path.iterdir())
_could_ end up both triggering and displaying an empty list in the
exception detail. The assignment-expression version cannot.
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