Typeerror字符串索引必须是整数，而不是STR python

Question

我定义了一个函数get_class_average()，有一个参数"students"。students是三个学生的列表:lloyd, alice, tyler，它们是间接字典。get_average()是一个计算平均值的函数，它工作得很好。当我尝试调用函数get_class_average()时，我得到错误:

typeerror string indices must be integers not str

我的代码

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!
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()函数期望传递整个学生列表，而不是每个学生。

删除for key in student:循环:

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

在get_class_average()函数中，您似乎太早返回;将return取消缩进，使其不属于循环。results.append()在改变results 时返回None :

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

这仍然不计算整个类的平均值，然而;它只是将每个学生的平均值收集到一个列表中。