text: I am trying to code my own food selector in python where people can pick if they want a tortilla in their wrap for example and the program will work out the costs.
  One of the extra's I am trying to do is that, if the customer does not want to checkout immediately they can save their order to a text file. That all works perfectly but how do I rename this text file to the
  user_name
  if order_save =="1":
  f = open ("user_name.txt","w")
  f.close()
  if Tortilla_option == "yes":
  f = open ("user_name.txt","a")
  f.write("Tortilla")
  f.close()
  if Chicken_option == "yes":
  f = open ("user_name.txt","a")
  f.write("\nChicken")
  f.close()
  if Salad_option == "yes":
  f = open ("user_name.txt","a")
  f.write("\nSalad")
  f.close()
  if Chilli_option == "yes":
  f = open ("user_name.txt","a")
  f.write("\nChilli Sauce")
  f.close()
  print ("Here is your takeway that will be saved",user_name,"!\n")
  f = open ("user_name.txt","r")
  print(f.read())
  f.close()
  Several things about this code. First:
  f = open ("user_name.txt","a") f.write("\nChilli Sauce") f.close()
  can be written as
  with open(user_name+'.txt', 'a') as f: f.write('\nChilli Saurce')
  that manages the closing of the file automatically. It's called a
  context manager
  Also, that saves the order into a file the name of which depends on who the user is. Notice that
  user_name is the variable, not a string.
  However, a better strategy would be do define a function:
  def write_order(user, item, option_yes_or_no): if option_yes_or_no=='yes': with open(user+'.txt', 'a') as f: f.write(item)
  and then you replace the whole thing with:
  for my_option in [tortilla_option, chicken_option, salad_option]: write_order(user_name, item, my_option)
  which avoids duplicating a lot of code.