Getting substring based on another column in a pandas dataframe

Question

Hi is there a way to get a substring of a column based on another column?

import pandas as pd
x = pd.DataFrame({'name':['bernard','brenden','bern'],'digit':[2,3,3]})
x

     digit  name
0   2   bernard
1   3   brenden
2   3   bern

What i would expect is something like:

for row in x.itertuples():
    print row[2][:row[1]]

be
bre
ber

where the result is the substring of name based on digit.

I know if I really want to I can create a list based on the itertuples function but does not seem right and also, I always try to create a vectorized method.

Appreciate any feedback.

Answer 1

Use apply with axis=1 for row-wise with a lambda so you access each column for slicing:

In [68]:
x = pd.DataFrame({'name':['bernard','brenden','bern'],'digit':[2,3,3]})
x.apply(lambda x: x['name'][:x['digit']], axis=1)

Out[68]:
0     be
1    bre
2    ber
dtype: object