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

[Andrew Barnert]

On Feb 12, 2016, at 12:58, Glenn Linderman <v+python at g.nevcal.com> wrote:
> 
>> On 2/12/2016 12:06 PM, Chris Barker wrote:
>> As for the SS# example -- it seems a bad idea to me to store a SS# number as an integer anyway -- so all the weird IDs etc. formats aren't really relevant...
> 
> SS#... why not integer?  Phone#... why not integer? There's a lot of nice digit-division conventions for phone#s in different parts of the world.

I'm the one who brought up the SSN example--and, as I said at the time, I almost certainly wouldn't have done that in Python. I was maintaining tests for a service that stored SSNs as integers (which I think is a mistake, but I couldn't change it), a automatically-generated strongly-typed interface to that service (which is good), and no easy way to wrap or hook that interface (which is bad). In Python, it's hard to imagine how I'd end up with a situation where I couldn't wrap or hook the interface and treat SSNs as strings in my test code. (In fact, for complicated tests, I did exactly that in Python to make sure they were correct, then ported them over to integrate with the test suite...)

And anyway, the only point was that I've actually used a grouping that isn't "every 3 digits" and it didn't end the world. I think everyone agrees that some such groupings will come up--even if not every specific examples is good, there are some that are. Even the people who want something more conservative than the PEP doesn't seem to be taking that position--they may not want double underscores, or "123_456_j", but they're fine with "if yuan > 9999_9999:".

So, either we try to anticipate every possible way people might want to group numbers and decide which ones are good or bad, or we just let the style guide say "meaningful group of digits" and let each developer decide what counts as "meaningful" for their application. Does anyone really want to argue for the former? 

If not, why not just settle that and go back to bikeshedding the cases that *are* contended, like "123_456_j"? (I'm happy either way, as long as the grammar rule is dead simple and the PEP 8 rule is pretty simple, but I know others have strong, and conflicting, opinions on that.)