[Python-Dev] Examples for PEP 572
jeanpierreda at gmail.com
Wed Jul 4 16:00:41 EDT 2018
On Wed, Jul 4, 2018 at 11:04 AM Steven D'Aprano <steve at pearwood.info> wrote:
> Did you actually mean arbitrary simple statements?
> if import math; mylist.sort(); print("WTF am I reading?"); True:
Yes. To quote PEP 572: "This is a tool, and it is up to the programmer
to use it where it makes sense, and not use it where superior
constructs can be used."
> A more reasonable suggestion would be to only allow *assignments*, not
> arbitrary simple statements. But that's another special case:
I don't agree that it is more reasonable, for exactly the reasons you
describe it to be surprising.
> with one or more semicolon-separated statements between the "if" and the
> if statement; statement; condition:
> If we stick to the rule that semicolons separate statements, that means
> we have:
> if statement # SyntaxError
> statement # okay
> condition: # SyntaxError
> If we don't want that, we need a new rule to treat semicolons
> differently inside if statements that they're treated elsewhere.
Yes. This is analogous to complaining that [1, 2, 3] should be a
syntax error because clearly this is a tuple with three elements:
"[1", "2", and "3]". In as far as it's a new parsing rule, it is a
"special case" indeed.
> If we applied this rule "allow statements separated by semicolons"
> everywhere, we'd get this:
Nobody said anything about allowing semicolon-delimited statements in
arbitrary places in the grammar.
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