Perform Calculation in Dataframe

i would like to perform a calculation for this DataFrame ['REGIS_HOUR']

If ['REGIS_HOUR'] is more than 12, then ['REGIS_HOUR']-12
but it doesn’t work. I did convert to int using astype('int')

>Solution :

Try this:

import numpy as np
df['REGIS_HOUR'] = np.where(df['REGIS_HOUR'] > 12, df['REGIS_HOUR'] -12, df['REGIS_HOUR'])