code academy: I am getting error- TypeError: string indices must be integers, not str

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=sum(numbers) total=float(total) total=total/len(numbers) return total

def get_average(student): homework=average(student["homework"]) quizzes=average(student["quizzes"]) tests=average(student["tests"]) return 0.1*homework+0.3*quizzes+0.6*tests

def get_class_average(students): results=[] for student in students: results.append(get_average([student])) print results return average(results)