Question

伙计们我刚刚开始学习Python ..我对它没有深刻的了解。我陷入了这个List和Dictionaries相关的问题..它向我显示了一条错误消息。错误O / P和代码在下面给出..

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

results.append(get_average(students))应该迭代列表，因为get_average需要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)

Answer 2

您的students变量是一个包含三名学生的列表（呃......三个词典）。

执行results.append(get_average(students));时，您将该列表传递给get_average方法，名为student的参数（但在get_average范围内，仍然是get_average列表，因为参数的名称无关紧要）

然后，在student['homework']中，您尝试将列表作为student进行访问。由于def get_class_average(students): results=[]; for student in students: results.append(get_average(student)); return average(results)参数是一个列表，这就是你得到错误的原因。

你可能想做这样的事情吗？

static class Extensions
{
    public static void Sort<T, TKey>(this ObservableCollection<T> collection, Func<ObservableCollection<T>, TKey> sort)
    {
        var sorted = (sort.Invoke(collection) as IOrderedEnumerable<T>).ToArray();
        for (int i = 0; i < sorted.Count(); i++)
            collection.Move(collection.IndexOf(sorted[i]), i);
    }
}

编辑（根据OP对此答案的评论）：

我认为好的资源可以是this和this（还有更多Googling python lists dictionaries）

Python：TypeError：list indices必须是整数，而不是string

2 个答案: