I want to create an additional feature(column) based on some manipulation of values from existing features
Welcome to the community! 

The code below is a starter. You can go on by naming the column and adding it to the original DataFrame:

import pandas as pd

data = pd.DataFrame({'x':[1,2,3], 'y':[10,20,30],'z':[100,200,300]})
print(data)
def my_fun(data,expression,variables):
    for v in variables:
        expression = expression.replace(v,'data.'+str(v))
    return eval(expression)


my_fun(data,'2*x+y',['x','y'])


output

   x   y    z
0  1  10  100
1  2  20  200
2  3  30  300

0    12
1    24
2    36
dtype: int64


There are two ways in general:


Use eval function to evaluate/execute expression in string form as I did.
Use symbolic libraries, most commonly used is SymPy, to use symbolics directly as variables.


Hope it helps. Good Luck!