Broadcasting issue with 2d index in DataFrames

[dbelgrod]

#Under pandas==0.23.0
import pandas
df1 = pd.DataFrame([[1]], columns = [[1]], index = [ 1, 2 ])
print(df1)
df2 = pd.DataFrame([[1]], columns = [[1]], index = [ [ 1, 2 ] ])
print(df2)

Output:
   1
1  1
2  1

ValueError: Shape of passed values is (1, 1), indices imply (1, 2)

#Under pandas==0.22.0, this issue did not arise.
import pandas
df1 = pd.DataFrame([[1]], columns = [[1]], index = [ 1, 2 ])
print(df1)
df2 = pd.DataFrame([[1]], columns = [[1]], index = [ [ 1, 2 ] ])
print(df2)
Output:
   1
1  1
2  1
   1
1  1
2  1

It seems that if the index is just a list then broadcasting the values occurs. If it a list of lists, the index still maintains the same shape but broadcasting is not done in this case.

Output of pd.show_versions()

pandas: 0.23.0 pytest: None pip: 18.1 setuptools: 40.6.3 Cython: None numpy: 1.11.3 scipy: 1.0.0 pyarrow: None xarray: None IPython: 7.2.0 sphinx: 1.8.2 patsy: 0.5.1 dateutil: 2.7.5 pytz: 2018.9 blosc: None bottleneck: 1.2.1 tables: 3.2.2 numexpr: 2.6.8 feather: None matplotlib: 3.0.1 openpyxl: None xlrd: 1.2.0 xlwt: None xlsxwriter: None lxml: None bs4: None html5lib: None sqlalchemy: 1.2.7 pymysql: None psycopg2: None jinja2: 2.10 s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: 0.7.0

[Liam3851]

I cannot reproduce under latest version 0.24.1:

In [1]: import pandas as pd

In [2]: df1 = pd.DataFrame([[1]], columns = [[1]], index = [ 1, 2 ])

In [3]: df1
Out[3]:
   1
1  1
2  1

In [4]: df2 = pd.DataFrame([[1]], columns = [[1]], index = [ [ 1, 2 ] ])

In [5]: df2
Out[5]:
   1
1  1
2  1

In [6]: pd.__version__
Out[6]: u'0.24.1'

Can you try the latest version?

[gfyoung]

@Liam3851 : I can't reproduce either. We should add the example as a test to close this unless someone can reproduce on the latest releases.

[jorisvandenbossche]

I can reproduce it. It was indeed failing on 0.23.4, but now working on 0.24.1. So indeed good to add a test for it.

However, do we actually want to support 2D input as columns / index ?

[jhereth]

Added tests in #29083. ci is failing (for unrelated reasons). Will try to re-push later.