I have a dataframe as below
A B C D E F G H I 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
I want to multiply every 3rd column after the 2 column in the last 2 rows by 5 to get the ouput as below.
How to acomplish this?
A B C D E F G H I 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 10 3 4 25 6 7 40 9 1 10 3 4 25 6 7 40 9
I am able to select the cells i need with df.iloc[-2:,1::3]
which results in the df as below but I am not able to proceed further.
B E H 2 5 8 2 5 8
I know that I can select the same cells with loc instead of iloc, then the calcualtion is straign forward, but i am not able to figure it out.
The column names & cell values CANNOT Be used since these change (the df here is just a dummy data)
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Answer
You can assign back to same selection of rows/ columns like:
df.iloc[-2:,1::3] = df.iloc[-2:,1::3].mul(5) #alternative #df.iloc[-2:,1::3] = df.iloc[-2:,1::3] * 5 print (df) A B C D E F G H I 0 1 2 3 4 5 6 7 8 9 1 1 2 3 4 5 6 7 8 9 2 1 2 3 4 5 6 7 8 9 3 1 2 3 4 5 6 7 8 9 4 1 2 3 4 5 6 7 8 9 5 1 10 3 4 25 6 7 40 9 6 1 10 3 4 25 6 7 40 9