Python:TypeError:列表索引必须是整数，而不是字符串

Question

伙计们，我刚开始学Python。。我对此一无所知。我把这张单子和字典有关的问题。。它向我显示了一条错误消息。 错误O/P和代码如下所示。。你知道吗

Error:
Traceback (most recent call last):
  File "python", line 48, in <module>
  File "python", line 45, in get_class_average
  File "python", line 25, in get_average
TypeError: list indices must be integers, not st




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]
}


def average(numbers):
    total = float(sum(numbers))/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_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"

get_letter_grade(get_average(lloyd))

def get_class_average(students):
    results=[];
    results.append(get_average(students));
    return average(results)

sts=[lloyd,alice,tyler];
get_class_average(sts)

Answer 1

您的students变量是一个包含三个学生的列表（呃。。。三本字典）。你知道吗

当您执行results.append(get_average(students));操作时，您将该列表传递给get_average方法，在一个名为student的参数中（但在get_average函数中，该函数仍然是一个列表，因为参数的名称是不相关的）

然后，在get_average中，您尝试以student['homework']的形式访问列表。因为student参数是一个列表，所以会出现错误。你知道吗

你可能想这样做？你知道吗

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

编辑（根据OP对该答案的评论）：

我想好的资源可以是this和this（还有更多的Googling python lists dictionaries）

Answer 2

results.append(get_average(students))应该在列表上迭代，因为get_average需要一个dict。替换为：

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

或者简单地说：

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