assert_frame_equal: "AssertionError: Attributes are different" is un-informative for DataFrames

[moi90]

Example from the docstring of assert_frame_equal

>>> from pandas.util.testing import assert_frame_equal
>>> df1 = pd.DataFrame({'a': [1, 2], 'b': [3, 4]})
>>> df2 = pd.DataFrame({'a': [1, 2], 'b': [3.0, 4.0]})
>>> assert_frame_equal(df1, df2)
Traceback (most recent call last):
AssertionError: Attributes are different
...
Attribute "dtype" are different
[left]:  int64
[right]: float64

Problem description

The AssertionError is un-informative in that it does not state the column for which the error happens.

Expected Output

Something like:

AssertionError: Attributes of "DataFrame.iloc[:, 1]" are different
...
Attribute "dtype" are different.

Output of pd.show_versions()

INSTALLED VERSIONS

commit : None
python : 3.6.7.final.0
python-bits : 64
OS : Linux
OS-release : 5.0.0-31-generic
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : de_DE.UTF-8
LOCALE : de_DE.UTF-8

pandas : 0.25.0
numpy : 1.17.2
pytz : 2019.3
dateutil : 2.8.0
pip : 19.2.3
setuptools : 41.4.0
Cython : 0.29.13
pytest : 5.2.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : 2.8.3 (dt dec pq3 ext lo64)
jinja2 : 2.10.3
IPython : 7.7.0
pandas_datareader: None
bs4 : None
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : None
matplotlib : None
numexpr : 2.7.0
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
s3fs : None
scipy : 1.3.1
sqlalchemy : 1.3.6
tables : 3.5.2
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None

Remedy

• assert_frame_equal passes obj="{obj}.iloc[:, {idx}]".format(obj=obj, idx=i) to assert_series_equal
• assert_series_equal should pass obj=Attributes of "{obj}".format(obj=obj) to assert_attr_equal