Vectorized Solution To Conditional Dataframe Selection

I recently asked a question which was answered - How do I add conditionally to a selection of cells in a pandas dataframe column when the the column is a series of lists?, but I b

Solution 1:

As Edchum says, vecorised solution can be problematic.

One non vectorized solution with apply custom functions:

df['e'] = df['d']

def exten(lst):
    return lst + [1]

def incre(lst):
    lst[-1] = lst[-1] + 1
    return lst

df.loc[df.a != df.b, 'd'] = df.e.apply(exten)
df.loc[df.a == df.b, 'd'] = df.e.apply(incre)
df = df.drop('e', axis=1)
print df
    a    b    c          d
0  On   On  [0]     [0, 4]
1  On  Off  [0]  [0, 1, 1]
2  On   On  [0]        [3]
3  On   On  [0]  [0, 4, 5]
4  On  Off  [0]     [0, 1]