Calculate new column as the mean of other columns pandas [duplicate]

Answer 1

Use .mean. By specifying the axis you can take the average across the row or the column.

df['average'] = df.mean(axis=1)
df

returns

       salary_1  salary_2  salary_3     average
0       230       235       210  225.000000
1       345       375       385  368.333333
2       222       292       260  258.000000

If you only want the mean of a few you can select only those columns. E.g.

df['average_1_3'] = df[['salary_1', 'salary_3']].mean(axis=1)
df

returns

   salary_1  salary_2  salary_3  average_1_3
0       230       235       210        220.0
1       345       375       385        365.0
2       222       292       260        241.0

Answer 2

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.