STY: Underscores for long numbers
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

lgtm if green See also the comments in https://github.com/pandas-dev/pandas/pull/30169#discussion_r355711538 yeah, I agree with @jorisvandenbossche (underscores only for 7+ digits), though I like having underscores in tests, as it helps when reading the tests. Hello @MomIsBestFriend! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

















There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-12-10 11:47:05 UTC Thanks @MomIsBestFriend 