typeerror字符串索引必須是整數，而不是str python

Question

我定義了一個具有一個參數“ students”的函數get_class_average() 。 students是3個學生的列表：lloyd，alice，tyler，它們是間接詞典。 get_average()是一個計算平均值的函數，它可以正常工作。 當我嘗試調用函數get_class_average()出現錯誤：

typeerror string indices must be integers not str

我的密碼

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!
from math import *
def average(numbers):
    total = sum(numbers)
    total = float(total)
    ans = total / len(numbers)
    return ans
num = [1,2,4,5,6]
a = average(num)
print a

def get_average(student):
    homework = average(student["homework"])
    quizzes = average(student["quizzes"])
    tests = average(student["tests"])
    sum = (0.1*homework) + (0.3 * quizzes) + (0.6 * tests)
    return sum

student = [lloyd, alice, tyler]
for key in student:   
    a = get_average(key)
    print a

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"

avg = get_average(lloyd)
t = get_letter_grade(avg)
print t


def get_class_average(students):
    results = []
    students = [lloyd, alice, tyler]
    a= get_average(students)
    r= results.append(a)
    return r

student = [lloyd, alice, tyler]
for key in student:   
    a = get_class_average(key)

print a

Answer 1

您的get_class_average()函數希望傳遞給整個學生列表，而不是每個學生。

刪除for key in student:的for key in student:循環：

students = [lloyd, alice, tyler]
a = get_class_average(students)

在get_class_average()函數中，您似乎返回得太早了 ； 使return不縮進不成為循環的一部分。 results.append()返回None ，因為它改變了results 就地 ：

def get_class_average(students):
    results = []
    for key in students:   
        a= get_average(key)
        results.append(a)
    return results

但是，這仍然不能計算出整個班級的平均水平。 它只是將每個學生的平均值收集到一個列表中。