BUG: Exception when calling pandas.isnull() with a pandas type object
State: closed

- [x] closes #27482 
- [x] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry


Labels:
name: Bug
name: Missing-data
description: np.nan, pd.NaT, pd.NA, dropna, isnull, interpolate
name: Error Reporting
description: Incorrect or improved errors from pandas

Comments:
Hello @pradeepb2505! 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:

* In the file [`pandas/core/dtypes/missing.py`](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/pandas/core/dtypes/missing.py):

> [Line 131:22](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/pandas/core/dtypes/missing.py#L131): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','

* In the file [`scripts/tests/test_27482.py`](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py):

> [Line 5:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L5): [E302](https://duckduckgo.com/?q=pep8%20E302) expected 2 blank lines, found 1
> [Line 6:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L6): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 6:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L6): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 7:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L7): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 7:2](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L7): [E117](https://duckduckgo.com/?q=pep8%20E117) over-indented
> [Line 8:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L8): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 8:3](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L8): [E117](https://duckduckgo.com/?q=pep8%20E117) over-indented
> [Line 8:19](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L8): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 8:21](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L8): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 8:23](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L8): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 9:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L9): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 10:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L10): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 10:23](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L10): [E225](https://duckduckgo.com/?q=pep8%20E225) missing whitespace around operator
> [Line 10:23](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L10): [E712](https://duckduckgo.com/?q=pep8%20E712) comparison to False should be 'if cond is False:' or 'if not cond:'
> [Line 10:30](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L10): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 12:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L12): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 13:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L13): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 13:3](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L13): [E117](https://duckduckgo.com/?q=pep8%20E117) over-indented
> [Line 13:30](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L13): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 13:32](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L13): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 13:34](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L13): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 14:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L14): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 15:1](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L15): [W191](https://duckduckgo.com/?q=pep8%20W191) indentation contains tabs
> [Line 15:23](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L15): [E225](https://duckduckgo.com/?q=pep8%20E225) missing whitespace around operator
> [Line 15:23](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L15): [E712](https://duckduckgo.com/?q=pep8%20E712) comparison to False should be 'if cond is False:' or 'if not cond:'
> [Line 15:30](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L15): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 19:20](https://github.com/pandas-dev/pandas/blob/380f2c0926fdbd969be928899cd74ecf2eb63b87/scripts/tests/test_27482.py#L19): [W292](https://duckduckgo.com/?q=pep8%20W292) no newline at end of file



##### Comment last updated at 2019-08-18 16:37:34 UTC
For any bugfix PR, you'll need to add a test for the fixed behavior in pandas/tests/
Thanks @pradeepb2505, besides adding the test, you'll have to run the two missing points in the checklist in the description. Thanks!
Sorry @pradeepb2505, this was fixed by https://github.com/pandas-dev/pandas/pull/27664. 

Let us know if you want help finding another issue to work on.
@TomAugspurger thank you for the information