[Python-ideas] Improve readability of long numeric literals

[Random832]

On Wed, Feb 10, 2016, at 12:42, Random832 wrote:
> 3__14159_26535_89793_84626

...And before anyone else points it out, I copied the fourth digit group
from the wrong position. (I happen to have the first 17 digits
memorized, so I typed the first three groups, and then mistakenly copied
from after the last one I had memorized rather than the last one I'd
typed).