Grouping And Auto Increment Based On Columns In Pandas

i have a pandas frame that looks like this: Is there a way to add the numbers in the last column without having to iterate through the data frame? I was playing with the results o

Solution 1:

In [10]: df['counter'] = df.groupby(['Product','SubProd']).cumcount()+1

In [11]: df
Out[11]: 
           Product SubProd  counter
4/20/2012        A      BL        1
4/27/2012        A      BL        2
5/4/2012         A      BL        3
5/11/2012        A      BL        4
5/18/2012        A      BL        5
4/20/2012        A      lk        1
4/27/2012        A      lk        2
5/4/2012         A      lk        3
5/11/2012        A      lk        4
5/18/2012        A      lk        5
5/25/2012        A      lk        6
10/31/2014       B      po        1
11/7/2014        B      po        2
11/14/2014       B      po        3
11/21/2014       B      po        4
11/28/2014       B      po        5