Create a binary file with roll number, name and marks. Input a roll number and update the marks

import os
from os.path import isfile

def create_file(roll_no, name, marks):
  #Check if file exists
  if isfile("students.txt"):
    #File Exists
    with open("students.txt", "a") as students_file:
      students_file.write("\n" + str(roll_no) + "\t" + name + "\t" + str(marks))
  else:
    #Create a new file
    with open("students.txt", "w") as students_file:
      students_file.write("Roll Number\tName\tMarks")
      students_file.write("\n" + str(roll_no) + "\t" + name + "\t" + str(marks))

def update_marks(roll_no, new_marks):
  with open("students.txt", "r") as students_file:
    lines = students_file.readlines()
  with open("students.txt", "w") as students_file:
    for line in lines