Remove blocks from GroupBy Code
Just trying to simplify things...

Currently fails (locally at least) with 5 tests, which interestingly enough seem mostly related to `mean`. Need to debug further but submitting now for feedback
Is the idea to operate column-by-column instead of block-by-block? > Is the idea to operate column-by-column instead of block-by-block?

I think that's what it will end up being. There are a lot of code paths in groupby that can be simplified and I *think* that iteration over elements is inconsistent. This is block iteration and we separately have iteration maybe by Series or Frame elements (depending on whether or not there are duplicate column labels) which makes the code harder to reason about and buggy

So not going strictly column by column in this PR yet; just removing what I think is a one-off code path to make things easier and will leave more for follow ups Hello @WillAyd! 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 2019-10-08 01:29:39 UTC Any idea of perf impact?  Presumably wide-block cases will be the hardest hit right? > Any idea of perf impact? Presumably wide-block cases will be the hardest hit right?

I think generally so yes, but unfortunately will depend on function (some don't go through the block management code). Once I get green in CI will run some tests and maybe add a few if coverage is bare, so will have something more tangible for you then This was a good exercise but I think need a few pre-cursors before coming back to this. Depending on how hard it is to rebase may ultimately end up with a new PR, but will see > This was a good exercise but I think need a few pre-cursors before coming back to this.

Definitely +1 on the concept.  Pending the performance hit, I'm looking forward to seeing this make a comeback. The more I work in/around this method, the more I think it needs to DIAF