marks.txt

Name--Maths--English--Science
Raju--60--50--70
Shyam--80--45--65
Baburao--40--40--40

result.py

marks = open("marks.txt", "r")
result_file = open("result.txt", "w")

line_number = 1
output = []

result_file.write("Name   Percentage \n")

for line in marks.readlines():
    line = line.replace("\n", "")
    if line_number != 1:
        result = line.split("--")
        name = result[0]

        math = float(result[1])
        english = float(result[2])
        science = float(result[2])

        percentage = ((math + english + science) / 300) * 100

        result_file.write(name + ' ' + str(percentage) + '\n')

    line_number += 1

marks.close()
result_file.close()