Hi pals, i've got the following error on my code and i can't figure out why it's wrong :

- string indices must be integers, not str -

What's my mistake?

```
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]
}
students= ["lloyd","alice","tyler"]
# Add your function below!
def average(numbers):
total = sum(numbers)
total = float(total)
total = total / len(numbers)
return total
def get_average (students):
homework = 0.1 * average(students["homework"])
quizzes = 0.3 * average(students["quizzes"])
tests = 0.6 * average(students["tests"])
weights_average = homework + quizzes + tests
return weights_average
def get_letter_grade(score) :
if score >= 90 :
return "A"
elif score >= 80 :
return "B"
elif score >= 70 :
return "C"
elif score >= 60 :
return "D"
else :
return "F"
def get_class_average (students) :
results = []
for student in students:
results.append(get_average(student))
return average(results)
print get_class_average(students)
print get_letter_grade(get_class_average(students))
```

Thanks in advance