how to concat sets when using groupby in pandas dataframe?

Question

This is my dataframe:

> df
       a             b
    0  1         set([2, 3])
    1  2         set([2, 3])
    2  3      set([4, 5, 6])
    3  1  set([1,         


        

Answer 1

This might be close to what you want

df.groupby('a').apply(lambda x: set.union(*x.b))

In this case it takes the union of the sets.

If you need to keep the column names you could use:

df.groupby('a').agg({'b':lambda x: set.union(*x)}).reset_index('a')

Result:

    a   b
0   1   set([1, 2, 3, 34])
1   2   set([2, 3])
2   3   set([4, 5, 6])