8.part of whole (help me pls)

display all the time: Oops, try again. get_class_average([alice]) resulted in an error: list indices must be integers, not str

What's wrong with my code?

```
Replace this line with your code.
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]
}
# Add your function below!
def average(numbers):
total = float(sum(numbers))
total = total / len(numbers)
return total
def get_average(student):
homework = float(sum(student["homework"]))/ len(student["homework"])
return 0.1 * average(student["homework"]) + 0.3 * average(student["quizzes"]) + 0.6 * average(student["tests"])
def get_letter_grade(score):
if score >= 90.0:
return "A"
elif score >= 80.0:
return "B"
elif score >= 70.0:
return "C"
elif score >= 60.0:
return "D"
else:
return "F"
print get_letter_grade(get_average(lloyd))
print get_letter_grade(get_average(alice))
print get_letter_grade(get_average(tyler))
def get_class_average(students):
results = []
for student in students:
get_average(students)
results.append(average)
return average(results)
```