็How to multiply specific range of data in dataframe python

as I already mentioned in the title.

For example, I have a dataframe in python like this :

dataframe = pd.DataFrame({‘Energy Consumption’: [20, 21, 19, 18, 25, 40, 18]})

If I want to multiply a number such as 0.3 on row index 3 to the end. How can I do that by the shortest operation time.

Thanks in advance.

>Solution :

You can do loc(assume the index is from 0 to n-1 , if not df.reset_index(drop=True, inplace=True) before below)

dataframe.loc[2:,'Energy Consumption'] *= 0.3
dataframe
   Energy Consumption
0                20.0
1                21.0
2                 5.7
3                 5.4
4                 7.5
5                12.0
6                 5.4