[Python-Dev] PEP 572: Why not := as standard assignment operator? (original) (raw)

Chris Angelico rosuav at gmail.com
Thu Apr 26 11:39:54 EDT 2018

On Fri, Apr 27, 2018 at 1:38 AM, Gustavo Carneiro <gjcarneiro at gmail.com> wrote:

On 26 April 2018 at 16:18, Chris Angelico <rosuav at gmail.com> wrote:

On Thu, Apr 26, 2018 at 11:13 PM, Martin Teichmann <lkb.teichmann at gmail.com> wrote: > Hi list, > > when reading PEP 572 I actually liked it a lot - I think it's actually > a cool idea. I think it's actually that cool an idea that it should be > made the default way of doing an assignment, over time phasing out the > good ole =. > > This would have several benefits: > > - people wouldn't have to worry about two different options > - different things would have a different look: assignment is :=, > keyword args is =, while comparison is ==. Especially beginners would > benefit from this clarity. > > in this case, for sure, we should make it possible to chain :=s, for > example by making it bind right-to-left, so that a := b := 3 would be > a := (b := 3) > > I'm sorry if somebody brought that up already, but the discussion has > grown so huge that I couldn't read through it entirely. It has indeed grown huge. And in the interests of not growing it even huger, I'm not going to rehash the arguments against making := into the one and only operator, save to say one thing: there's no way that "x = 1" can be removed from the language any time soon, and by "soon" I mean even by the Yes Prime Minister definition, where "any day now", in strategic terms, meant "within the next half century". In the interest of that, do you think := can be made illegal, by the grammar, if used outside an expression? a = 1 # legal a := 1 # Syntax error if a := 1: # legal

No. Any expression may be used as a statement, so this isn't "outside an expression".

ChrisA

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