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PEP 572: Python assignment expressions has been accepted

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317 points est | 3 comments | 03 Jul 18 08:30 UTC | HN request time: 0.617s | 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.
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1. arketyp ◴[03 Jul 18 09:33 UTC] No.17448736[source]▶
>You could argue everything above machine language is syntactic sugar.

The sugar is sprinkled on top of syntax, the stuff the parser deals with. Typing a += 1 instead of a = a + 1 is sugar because it parses the same. This assignment syntax seems different. IMHO.

replies(1): >>17449560 #
2. blattimwind ◴[03 Jul 18 12:27 UTC] No.17449560[source]▶
> because it parses the same

Does not. One is addition, the other is in-place addition; they're different things and can behave differently. E.g. in "a += b" and "a = a + b", the former might not construct an intermediate object, but mutate the existing a.

replies(1): >>17450607 #
3. ben-schaaf ◴[03 Jul 18 14:45 UTC] No.17450607[source]▶
To be more specific for python: "a += b" -> "a = a.__iadd__(b)" "a = a + b" -> "a = a.__add__(b)"

"__iadd__" and "__add__" can do whatever they want.