Guys this is my code, could someone help me out?

```
students=[lloyd,alice,tyler]
def get_class_average(students):
results=[]
for student in students:
results.append(get_average(students))
return average(results)
print get_class_average(students)
print get_letter_grade(get_class_average(students))
```

This is my error message: Oops, try again. get_class_average([alice]) resulted in an error: list indices must be integers, not str