BUG: groupby with levels on duplicated multi-index

[vumaasha]

x = pd.DataFrame({'x':[1,1,3,3],'y':[3,3,5,5]},index=[11,11,12,12])
y = x.stack()
print(y)
print(y.groupby(level=[0,1]).sum())

Ouput

11  x    1
    y    3
    x    1
    y    3
12  x    3
    y    5
    x    3
    y    5
dtype: int64
11  x    1
    y    3
    x    1
    y    3
12  x    3
    y    5
    x    3
    y    5
dtype: int64

The stack and group by sum are just the same.

Expected output:

11  x    2
11  y    6
12  x    6
12  y    10

[jreback]

yep, looks a little buggy. As the following gives the expected output.

In [5]: y.reset_index().groupby(['level_0','level_1']).sum()
Out[5]: 
                  0
level_0 level_1    
11      x         2
        y         6
12      x         6
        y        10