Convert DataFrameGroupBy object to DataFrame pandas

 df_g.apply(lambda x: x) 

will return the original dataframe.

The result of kl.aggregate(np.sum) is a normal DataFrame, you just have to assign it to a variable to further use it. With some random data:

>>> df = DataFrame({'A' : ['foo', 'bar', 'foo', 'bar',
>>>                         'foo', 'bar', 'foo', 'foo'],
...                  'B' : ['one', 'one', 'two', 'three',
...                         'two', 'two', 'one', 'three'],
...                  'C' : randn(8), 'D' : randn(8)})
>>> grouped = df.groupby('A')
>>> grouped
<pandas.core.groupby.DataFrameGroupBy object at 0x04E2F630>
>>> test = grouped.aggregate(np.sum)
>>> test
            C         D
A                      
bar -1.852376  2.204224
foo -3.398196 -0.045082

Using pd.concat, just like this:

   pd.concat(map(lambda x: x[1], groups))

Or also keep index aligned:

   pd.concat(map(lambda x: x[1], groups)).sort_index()