[Python-Dev] PEP 515: Underscores in Numeric Literals

[Andrew Barnert]

On Feb 11, 2016, at 02:13, Steven D'Aprano <steve at pearwood.info> wrote:
> 
>> On Wed, Feb 10, 2016 at 08:41:27PM -0800, Andrew Barnert wrote:

>> They're both presented as something the syntax allows, and neither one 
>> looks like something I'd ever want to write, much less promote in a 
>> style guide or something, but neither one screams out as something 
>> that's so heinous we need to complicate the language to ensure it 
>> raises a SyntaxError. Yes, that's my opinion, but do.you really have a 
>> different opinion about any part of that?
> 
> I don't think the rule "underscores must occur between digits" is 
> complicating the specification.

That rule isn't in the specification in the PEP, except as one of the alternatives rejected for being "too restrictive". It's also not the rule you were suggesting in your previous email, arguing where you insisted that you wanted something "more liberal". I also don't understand why you're presenting this whole thing as an argument against my response, which was suggesting that whatever rule we choose should be simpler than what's in the PEP, when that's also (apparently, now) your position.

> It is *less* complicated to explain this 
> rule than to give a whole lot of special cases

Sure. Your rule is about as complicated as the Swift rule, and both are much less complicated than the PEP. I'm fine with either one, because, as I said, the edge cases don't matter to me nearly as much as having a rule that's easy to keep it my head and easy to lex. The only reason I specifically proposed the Swift rule instead of one of the other simple rules is that it seemed the most "liberal", which the PEP was in favor of, and and it has precedent in more other languages. But, in favor of your version, almost every language uses some variation of "you can put underscores between digits" as the "tutorial-level" explanation and rationale.