[Python-Dev] Assignment expression and coding style: the while True case (original) (raw)

Nathaniel Smith njs at pobox.com
Wed Jul 4 19:15:41 EDT 2018

On Wed, Jul 4, 2018 at 3:51 PM, Victor Stinner <vstinner at redhat.com> wrote:

My question is now: for which "while True" patterns are the assignment expression appropriate? There identified different patterns.

== Pattern 1, straighforward == while True: line = input.readline() if not line: break ... IMHO here assingment expression is appropriate here. The code remains straighfoward to read. while (line := input.readline()): ...

There are some obvious caveats here – no-one has real experience with := yet, so any opinions right now are informed guesswork that will probably change some if/when we get more experience with it. Also, the stdlib is a big place, and it seems inevitable that maintainers of different modules will have different preferences. So I don't think it makes sense to try to define some Official Universal Rule about when := is appropriate and when it isn't.

That said, FWIW, my current feeling is that this simplest case is the only one where I would use :=; for your other examples I'd stick with the loop-and-a-half style.

-n

-- Nathaniel J. Smith -- https://vorpus.org

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