assert_frame_equal not differentiating NaN and None within object dtype #18463
Description
Code Sample, a copy-pastable example if possible
df1 = pd.DataFrame([['foo', 'bar', 'baz'], [None, None, None]]) df2 = pd.DataFrame([['foo', 'bar', 'baz'], [np.nan, np.nan, np.nan]]) tm.assert_frame_equal(df1, df2)Problem description
No AssertionError gets raised in this case, even though I would not expect None and np.nan to be considered equal values (I found this while testing #18450)
Note that if you simply compared a DataFrame with only np.nan with another containing only None you would get an AttributeError that the dtypes are different (float64 vs object) but because the missing values are mixed into object dtypes here I think that differentiation gets lost
Expected Output
AssertionError: DataFrame.iloc[1, :] are different Output of pd.show_versions()
[paste the output of pd.show_versions() here below this line]
INSTALLED VERSIONS
commit: d64995a
python: 3.6.2.final.0
python-bits: 64
OS: Darwin
OS-release: 17.2.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8
pandas: 0.22.0.dev0+205.gd64995a4f
pytest: 3.2.5
pip: 9.0.1
setuptools: 36.4.0
Cython: 0.26
numpy: 1.13.1
scipy: None
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: 1.6.3
patsy: None
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None