清华大佬耗费三个月吐血整理的几百G的资源，免费分享！....>>>

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)
    result = total/len(numbers)
    return result
    
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_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)
    
students=[lloyd, alice, tyler]
print get_class_average(students)
print get_letter_grade(get_class_average(students))