codecademy 第一次大作业答案（计算平均成绩）

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))
    return total/len(numbers)

def get_average(student):

    return 0.1 * average(student["homework"]) + \
        0.3 * average(student["quizzes"]) + \
        0.6 * average(student["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 item in students:
        studentAvg = get_average(item)
        results.append(studentAvg)
    return average(results)

students = [lloyd,alice,tyler]
print (get_class_average(students))
print (get_letter_grade(get_class_average(students)))