Let me start out by first stating that I have read through a dozen posts comparing my code to what everyone else has posted. Besides some difference in variable names, my code looks identical.

Exercise link : https://www.codecademy.com/courses/python-beginner-en-qzsCL/1/4?curriculum_id=4f89dab3d788890003000096

My code throws the following error:

Oops, try again. get_class_average([alice]) resulted in an error: unsupported operand type(s) for +: 'int' and 'NoneType'

I've compared the functions to what others have posted and it seems correct.

```
lloyd = {
"name": "Lloyd",
"homework": [90.0, 97.0, 75.0, 92.0],
"quizzes": [88.0, 40.0, 94.0],
"tests": [75.0, 90.0]
}
alice = {
"name": "Alice",
"homework": [100.0, 92.0, 98.0, 100.0],
"quizzes": [82.0, 83.0, 91.0],
"tests": [89.0, 97.0]
}
tyler = {
"name": "Tyler",
"homework": [0.0, 87.0, 75.0, 22.0],
"quizzes": [0.0, 75.0, 78.0],
"tests": [100.0, 100.0]
}
def average(numbers):
total = float(sum(numbers))
total = total / len(numbers)
return total
def get_average(student):
homework = average(student['homework'])
quizzes = average(student['quizzes'])
tests = average(student['tests'])
score = ((homework * .1) + (quizzes * .3) + (tests * .6))
def get_letter_grade(score):
if (score >= 90.0):
return "A"
elif(score >= 80.0 and score < 90.0):
return "B"
elif(score >= 70.0 and score < 80.0):
return "C"
elif(score >= 60.0 and score < 70.0):
return "D"
else:
return "F"
def get_class_average(students):
results = []
for pupil in students:
results.append(get_average(pupil))
return average(results)
```

Any help would be much appreciated.