BUG: pd.NA acts differently when inside/outside a series/dataframe with object dtype

[HYChou0515]

Code Sample, a copy-pastable example if possible

# return pd.NA, cool
pd.NA | pd.NA

# return False, not cool
pd.Series([pd.NA]) | pd.Series([pd.NA])

Problem description

pd.NA acts differently when inside/outside a series/dataframe may be confusing. It force me to handle each entry of a series/dataframe.

Expected Output

Output of pd.show_versions()

INSTALLED VERSIONS

commit : None
python : 3.8.1.final.0
python-bits : 64
OS : Linux
OS-release : 4.15.0-91-generic
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : en_US.UTF-8
LANG : en_US.UTF-8
LOCALE : None.None

pandas : 1.0.1
numpy : 1.18.1
pytz : 2019.3
dateutil : 2.8.1
pip : 20.0.2
setuptools : 45.2.0
Cython : None
pytest : 5.3.5
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 2.11.1
IPython : 7.12.0
pandas_datareader: None
bs4 : None
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : None
matplotlib : 3.2.0
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
pytest : 5.3.5
pyxlsb : None
s3fs : None
scipy : 1.4.1
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None
numba : None

[TomAugspurger]

You've created an object-dtype Series

In [4]: pd.Series([pd.NA])
Out[4]:
0    <NA>
dtype: object

If you create a boolean Series with dtype='boolean' you'll get the expected result.

Fixing this may be possible, but I don't think it should be a high priority.

[jorisvandenbossche]

Given the several issues with pd.NA in object dtype, should we consider warning about it? (cfr #32931)

[TomAugspurger]

By warning, do you mean something in the docs or in code?

+1 to something in the docs. I don't think there's any good reason to end up with an NA in object dtype.

For code, detecting NA would be difficult / slow.