Newbee needs Help ref Using Function Statements not Loops(For)

[jstreet10]

How would i use function statements instead of loops(for) in this code? i
have tried some, but not working.

#  this program is suppose to read fm a file, computes the     average and
reads fm a file
#  file grade info: dave, 75; david, 70; davy, 60; john, 70; jon, 60; nina,
55; nino, 50; ray, 65; sherry, 90; terry, 85

import os, sys, string
student_table  = {}
grade_counter = 0
input_file = open("grades.txt","r")
sum = 0
for record in input_file.readlines():
     grade_counter += 1
     record_key , record_value = string.split(record,",")
     student_table[record_key] = record_value
     sum += int (record_value)
average = sum/grade_counter

input_file.close()
student_names = student_table.keys()
student_names.sort()
output_file = open("processed.txt", "w")

for student_name in student_names:
     output_file.write(student_name +"," + student_table
           [student_name])
output_file.write("Average grade is" + str(average))
output_file.close()