[Python-Dev] Examples for PEP 572 (original) (raw)

Devin Jeanpierre 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: pass

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 condition:

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: [snip]

Nobody said anything about allowing semicolon-delimited statements in arbitrary places in the grammar.

-- Devin

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