TYP: pandas/core/frame.py
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I plan to do a pass through the whole file - putting it up in case anybody has feedback on what I have
suggest that you do reasonably sized pieces so this doesn't sit in review for too long - better multiple but smaller prs as this is a huge file cc @simonjayhawkins @WillAyd  > would prefer you don't mix easy and hard ones. e.g. a pass on bool / strings ones. and Axis / Level. These are easy to review. by mixing lots of things its very hard to give good scrutiny here.
> 
> would prefer that.

For sure. I'll keep the hard ones that I've already attempted here so all the comments are in one place. I'll resubmit easy and follow-ons in separate PRs needs merge master and will look mypy green + all comments addressed (or moved out to orthogonal PRs) Green + addressed comments This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. @arw2019 if you want to merge master and update (or close and open a new one ok too) @jreback @simonjayhawkins updated, CI green, comments addressed > @jreback @simonjayhawkins updated, CI green, comments addressed

ok. maybe we should merge this. there has been plenty of discussion here. @jreback @WillAyd i'm merging later today if no objections.

mypy is green and typing PRs easily become stale or get abandoned.

There are no ignores, casts or asserts added here and no existing annotations changed/deleted.

if any of the typing additions added here are problematic they will be picked up by mypy as more types are added.


 sure let's make sure this is rebased first  yep did that locally and ran mypy before I commented. will push and merge on green Thanks @arw2019 