an easy way to solve this problem is shown below :
col = df.loc[: , "salary_1":"salary_3"]
where "salary_1" is the start column name and "salary_3" is the end column name
df['salary_mean'] = col.mean(axis=1)
df
This will give you a new dataframe with a new column that shows the mean of all the other columns
This approach is really helpful when you are having a large set of columns or also helpful when you need to perform on only some selected columns not on all.
