Cumulative operations on dtype objects

Question

I am trying to figure out how I can apply cumulative functions to objects. For numbers there are several alternatives like cumsum and cumcount. The

Answer 1

I think you can use cumsum with exception set, then you need first convert to list and then to set. Btw, storing set (C2) or lists of lists (C4) in columns in DataFrame is not recommended.

print df
   C1   C2 C3   C4
0   1  {A}  A  [A]
1   2  {B}  B  [B]
2   3  {C}  C  [C]
3   4  {D}  D  [D]

print df[['C1','C3','C4']].cumsum()
   C1    C3            C4
0   1     A           [A]
1   3    AB        [A, B]
2   6   ABC     [A, B, C]
3  10  ABCD  [A, B, C, D]

df['C2'] = df['C2'].apply(list)
df = df.cumsum()
df['C2'] = df['C2'].apply(set)
print df
   C1            C2    C3            C4
0   1           {A}     A           [A]
1   3        {A, B}    AB        [A, B]
2   6     {A, C, B}   ABC     [A, B, C]
3  10  {A, C, B, D}  ABCD  [A, B, C, D]