Codecademy，Python - “'NoneType' 对象不可迭代”

Question

当我执行下面的代码时。我收到此错误消息

get_class_average([alice]) resulted in an error: 'NoneType' object is not iterable

有人可以帮助我吗？

代码

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)/1
    total = total/int(len(numbers))
    return total
def get_average(l_student):
    homework = average(l_student["homework"]) * 0.1
    quizzes = average(l_student["quizzes"]) * 0.30
    tests = average(l_student["tests"]) * 0.6
    media = homework + quizzes + tests
    return media
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 i in students:
        results = results.append(get_average(i))
    return average(results)

Answer 1

append 修改它被调用的列表和 returns None。因此，而不是

for i in students:
    results = results.append(get_average(i))

您应该只调用 append，而不是在任何地方分配它的（无用的）return 值：

for i in students:
    results.append(get_average(i))

Codecademy，Python - “'NoneType' 对象不可迭代”

Codeacademy, Python - "'NoneType' object is not iterable"

python

nonetype