CLN: Finish isort core
- [x] xref #23334
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Hello @alimcmaster1! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/conftest.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/conftest.py) !

 - There are no PEP8 issues in the file [`pandas/core/algorithms.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/algorithms.py) !

 - There are no PEP8 issues in the file [`pandas/core/api.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/api.py) !

 - There are no PEP8 issues in the file [`pandas/core/apply.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/apply.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/base.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/categorical.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/categorical.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimelike.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/datetimelike.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimes.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/integer.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/integer.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/interval.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/interval.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/period.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/period.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/timedeltas.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/arrays/timedeltas.py) !

 - There are no PEP8 issues in the file [`pandas/core/base.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/categorical.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/categorical.py) !

 - There are no PEP8 issues in the file [`pandas/core/common.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/common.py) !

 - There are no PEP8 issues in the file [`pandas/core/config.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/config.py) !

 - There are no PEP8 issues in the file [`pandas/core/config_init.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/config_init.py) !

 - There are no PEP8 issues in the file [`pandas/core/frame.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/frame.py) !

 - There are no PEP8 issues in the file [`pandas/core/generic.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/generic.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/accessors.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/accessors.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/api.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/api.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/base.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/category.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/category.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/frozen.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/frozen.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/interval.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/interval.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/multi.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/multi.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/numeric.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/numeric.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/period.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexes/period.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexing.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/indexing.py) !

 - There are no PEP8 issues in the file [`pandas/core/internals/blocks.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/internals/blocks.py) !

 - There are no PEP8 issues in the file [`pandas/core/internals/concat.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/internals/concat.py) !

 - There are no PEP8 issues in the file [`pandas/core/internals/managers.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/internals/managers.py) !

 - There are no PEP8 issues in the file [`pandas/core/missing.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/missing.py) !

 - There are no PEP8 issues in the file [`pandas/core/nanops.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/nanops.py) !

 - There are no PEP8 issues in the file [`pandas/core/ops.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/ops.py) !

 - There are no PEP8 issues in the file [`pandas/core/panel.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/panel.py) !

 - There are no PEP8 issues in the file [`pandas/core/resample.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/resample.py) !

 - There are no PEP8 issues in the file [`pandas/core/sorting.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/sorting.py) !

 - There are no PEP8 issues in the file [`pandas/core/sparse/api.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/sparse/api.py) !

 - There are no PEP8 issues in the file [`pandas/core/sparse/frame.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/sparse/frame.py) !

 - There are no PEP8 issues in the file [`pandas/core/sparse/scipy_sparse.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/sparse/scipy_sparse.py) !

 - There are no PEP8 issues in the file [`pandas/core/sparse/series.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/sparse/series.py) !

 - There are no PEP8 issues in the file [`pandas/core/strings.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/strings.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/datetimes.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/tools/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/numeric.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/tools/numeric.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/timedeltas.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/tools/timedeltas.py) !

 - There are no PEP8 issues in the file [`pandas/core/util/hashing.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/util/hashing.py) !

 - There are no PEP8 issues in the file [`pandas/core/window.py`](https://github.com/alimcmaster1/pandas/blob/35a1a819942f227f2268173d1cabc75829aae4df/pandas/core/window.py) !

 Thanks for taking a look @WillAyd just actually removed a bunch of files to aid reviewing this thanks @alimcmaster1 

btw these are going really well, don't mind having more files in each PR. ping on green. small linting issue in the 3.6 build

run

``LINT=1 ci/code_checks.sh`` # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=h1) Report
> Merging [#23765](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/84cc0fb71393b685a28afc6bfe323a782296e455?src=pr&el=desc) will **increase** coverage by `0.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23765/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23765      +/-   ##
==========================================
+ Coverage   92.27%   92.28%   +0.01%     
==========================================
  Files         161      161              
  Lines       51411    51449      +38     
==========================================
+ Hits        47439    47481      +42     
+ Misses       3972     3968       -4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.68% <100%> (+0.01%)` | :arrow_up: |
| #single | `42.28% <100%> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/sparse/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3BhcnNlL2ZyYW1lLnB5) | `94.86% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2Jhc2UucHk=) | `97.35% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `95.96% <100%> (-0.19%)` | :arrow_down: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.67% <100%> (ø)` | :arrow_up: |
| [pandas/core/sparse/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3BhcnNlL3Nlcmllcy5weQ==) | `95.53% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.44% <100%> (-0.01%)` | :arrow_down: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `96.09% <100%> (+0.45%)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `98.51% <100%> (ø)` | :arrow_up: |
| [pandas/core/sparse/scipy\_sparse.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3BhcnNlL3NjaXB5X3NwYXJzZS5weQ==) | `97.05% <100%> (ø)` | :arrow_up: |
| [pandas/core/tools/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvdGltZWRlbHRhcy5weQ==) | `98.03% <100%> (ø)` | :arrow_up: |
| ... and [17 more](https://codecov.io/gh/pandas-dev/pandas/pull/23765/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=footer). Last update [84cc0fb...5fe038e](https://codecov.io/gh/pandas-dev/pandas/pull/23765?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @alimcmaster1 