[Python-Dev] PEP 572 and assert (original) (raw)
Guido van Rossum guido at python.org
Tue Jul 17 10:59:35 EDT 2018
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On Tue, Jul 17, 2018 at 1:50 AM, Serhiy Storchaka <storchaka at gmail.com> wrote:
Recently Barry shown an example:
assert len(subdirs := list(path.iterdir())) == 0, subdirs It looks awful to me. It looks even worse than using asserts for validating the user input. The assert has a side effect, and it depends on the interpreter option (-O). Even if subdirs is not used outside of the assert now, it is easy to introduce an error later, and it is hard to notice it if tests are not ran with the -O option regularly. Does PEP 572 encourages writing such code, discourages this, or completely forbids?
The PEP has no specific opinion except it is not forbidden.
Personally I like Barry's example just fine -- assuming subdirs is not
used later, this feels like a good use case.
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