Asking for grades and then averaging them.

gistfile1.py

done = False
grades = []

while not done:
  yesno = raw_input("\nDo you have a grade to enter?: ")
  if str(yesno).lower() in ["yes", "y"]:
    input = raw_input("\nEnter Grade: ")
    try:
       val = float(input)
    except ValueError:
       print("\nThat's not an int!")
    else:
      grades.append(float(input))
  else:
    done = True
    print "\nYour average is: " + str(sum(grades)/len(grades))

The float() function in grades.append(float(input)) seems redundant but too lazy to change it now.