Python: Convert a Letter Grade to its corresponding integer value

Question

I am attempting to troubleshoot the errors in this code.

The program is supposed to handle as many students as the user indicates are in the class. Receive a letter grade: A, B, C, D, F for each student. Finally it will calculate and display the class average.

My code so far:

students = int(input('How many students: '))
total_sum = 0
for n in range(students):
    Letter = input('Enter grades: ')
    Letter_int = Letter
if Letter == "A":
    Letter_int == int(80)
elif Letter == "B":
    Letter_int == int(70)
elif Letter == "C":
    Letter_int == int(60)
elif Letter == "D":
    Letter_int == int(50)
elif Letter == "F":
    Letter_int == int(40)
    total_sum += Letter_int
avg = total_sum/students
print('Average of this/these', students, 'student(s) is:', avg)

The code isn't adding the integer value of the letter grades, the sum always returns as 0 or TypeError: unsupported operand type(s) for +=: 'int' and 'str'. I am a python novice and I could use some assistance.

you should rethink your indentation... (the `if/elif` should be in the loop: the `total_sum += Letter_int` should be at the end of the loop - outside the `elif` clause). — hiro protagonist, Oct 09 '19 at 18:11
You need to revisit your class materials on writing a loop. The loop you have runs through all of the input, but throws away all but the last grade entered. *Then* your code checks that one letter grade. *Only* in the case of a final `F` do you add anything to `total_sum`. See this lovely [debug](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/) blog for help. First and foremost, insert some `print` statements to trace program flow and value. — Prune, Oct 09 '19 at 18:12
Possible duplicate of [Why does my "if" statement in python not work?](https://stackoverflow.com/questions/58140843/why-does-my-if-statement-in-python-not-work) — Trenton McKinney, Oct 09 '19 at 18:14

score 0 · Accepted Answer · answered Oct 09 '19 at 18:54

Here is your code improved and made work. Use it, but please read the comments I provided and analyze what parts I have changed. Also, it would be good to revise Python documentation as others mentioned. Especially indentation and it's meaning in Python.

students = int(input('How many students: '))
total_sum = 0
for n in range(students):
    Letter = input('Enter grades: ')
    Letter_int = 0 # here you better initialize with integer not string
    if Letter == "A": # this condition needs to be indented - you want it to be executed
                      # in every iteration of for loop
        Letter_int = 80 # the assignment in Python is done by "=" not "==" (that would be comparison) 
    elif Letter == "B": 
        Letter_int = 70 # you do not need to do int(70), 70 is already an integer
    elif Letter == "C":
        Letter_int = 60
    elif Letter == "D":
        Letter_int = 50
    elif Letter == "F":
        Letter_int = 40
    total_sum += Letter_int # this cannot happen inside elif clause - this way it would only be
                            # executed when F grade is provided
    avg = total_sum/students
    print('Average of this/these', students, 'student(s) is:', avg)

Python: Convert a Letter Grade to its corresponding integer value

1 Answers1