Suppose I have the following dataframe and series:
In [20]: df = pd.DataFrame(np.ones((3,4)), columns=pd.MultiIndex.from_product([['A', 'B'],['a', 'b']]))
In [21]: s = pd.Series({'a':1, 'b':2})
In [22]: df
Out[22]:
A B
a b a b
0 1 1 1 1
1 1 1 1 1
2 1 1 1 1
In [23]: s
Out[23]:
a 1
b 2
dtype: int64
Trying to multiply this by the columns, and matching on the second level, gives the following error:
In [24]: df.mul(s, axis=1, level=1)
...
File "C:\Anaconda\lib\site-packages\pandas\core\index.py", line 1786, in _join_multi
raise ValueError("cannot join with no level specified and no overlapping names")
ValueError: cannot join with no level specified and no overlapping names
In any case, this is a wrong error message, as I did specify a level.
Further, this does work and gives the expected output with a named level instead of a integer level:
In [25]: df2 = df.copy()
...: df2.columns.names = ['l0', 'l1']
In [35]: df2.mul(s, axis=1, level='l1') # <-- works
Out[35]:
l0 A B
l1 a b a b
0 1 2 1 2
1 1 2 1 2
2 1 2 1 2
Am I correct that this should also work with integer levels?
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