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PEP 572: Python assignment expressions has been accepted

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317 points est | 1 comments | 03 Jul 18 08:30 UTC | HN request time: 0.314s | source
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gbfowler ◴[03 Jul 18 09:04 UTC] No.17448582[source]▶
It is not syntactic sugar, "x := 10" is an assignment expression in contrast with "x = 10", which is a statement.

Hence the former can be used in contexts like "if x := 10: pass", which is the whole point of the PEP.

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Aardwolf ◴[03 Jul 18 09:14 UTC] No.17448624[source]▶
Why is it not syntactic sugar? It looks like convenience. You could argue everything above machine language is syntactic sugar.
replies(5): >>17448721 #>>17448736 #>>17448847 #>>17448880 #>>17448984 #
akvadrako ◴[03 Jul 18 09:30 UTC] No.17448721[source]▶
Not so. Many things change the semantics, otherwise high level languages would just be glorified macros.

For example, import mod is NOT defined as

  mod = eval(open("mod.py").read())
but involves abstract load module operation, which is dependant on the environment.

That's why := is just syntactic sugar; there are no new semantics.

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1. dragonwriter ◴[03 Jul 18 15:21 UTC] No.17450904[source]▶
> That's why := is just syntactic sugar; there are no new semantics.

There seem to be new semantics in the interaction with comprehensions, which is one of the main sources of controversy in the discussion these linked as the OP.