[Python-Dev] PEP 572: Do we really need a ":" in ":="?

Alexander Belopolsky alexander.belopolsky at gmail.com
Thu Jul 5 19:58:00 EDT 2018

On Thu, Jul 5, 2018 at 7:47 PM Yury Selivanov <yselivanov.ml at gmail.com>

> I think I tried a variation of your proposal here
> https://mail.python.org/pipermail/python-dev/2018-April/152939.html
> and nobody really liked it.
> Right. I now recall your proposal.  I think I did not support it at the
time because I was against having expressions with side-effects regardless
of syntax.  Now, as I mentioned, in the current form the PEP makes a strong
case for allowing a limited form of variable assignment in expressions.  I
also think that the dreadfulness of mistyping = where == is expected is
exaggerated.  In all motivating cases, := is used to introduce new bindings
rather than rebinding existing names.  Automated code checkers can easily
warn users when they rebind variables in if statements and suggest that
they silence the warnings with redundant (..) if they really want what they
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