In [1]: import pandas as pd
In [2]: df = pd.DataFrame({'raw': ['1,2,3', '3,4,5']})
In [3]: df
Out[3]:
raw
0 1,2,3
1 3,4,5
In [4]: df['col1']=df['raw'].str.split(',').str.get(0)
In [5]: df['col2']=df['raw'].str.split(',').str.get(1)
In [6]: df['col3']=df['raw'].str.split(',').str.get(2)
In [7]: df
Out[7]:
raw col1 col2 col3
0 1,2,3 1 2 3
1 3,4,5 3 4 5