如何使用Python查找平均值？

Question

I have to find the average scores of a class of students. I want to do this by finding an average of each student and finding the average of those averages. I have everything else in the program working perfectly, except for this block:

def get_class_average(class_list): total = 0 for student in class_list: student = student["name"] get_average(student) total_class += get_average(student)

I can give you the rest of the code if someone asks, but I know it's probably that paragraph. Here's my error:

get_class_average([lloyd]) returned 85.85 instead of 80.55 as expected

So I'm doing something mathematically incorrect. I believe the problem is that I'm trying to do this with a for loop. How would you find the correct average of an entire class?

edit:

Here is another function I have in the code. It's not the only other one, but it is where my error says it would be:

# Add your function below!
def average(numbers):
    total = sum(numbers)
    total = float(total)
    total /= len(numbers)
    return total

I think there's an error with the function for that reason.

Here is the whole code in case you want to look at it:

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]
}

results = []

# Add your function below!
def get_average(numbers):
    for total in numbers:
        total += total
        total *= 1.0
    total /= len(numbers)
    return total

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(class_list): total = 0 for student in class_list: student = student["name"] get_average(student) total_class += get_average(student)

return average(class)

Answer 1

Without knowing your functions it's a little hard to debug. I'm also wondering why you have a function get_average AND a function average . Anyway, I bet the error is that you return average(b) in your first code example as opposed to average(results) . Also, this statement would need one less level of indentation, or else your for loop will never go beyond the first x in students . Currently, you are just returning average(get_average(x)) where x is the first item in students .

Your second function is closer, the final return statement just needs one level less of indentation and you need to initialize results . Try this:

def get_class_average(students):
    results = [] # initialize results
    for result in students:
        result = get_average(result)
        results.append(result)
    return average(results) # not part of the for looop