# Part of a while

#1

I've got this...
get_class_average([alice]) resulted in an error: unsupported operand type(s) for +: 'int' and 'NoneType'

My code's below

``````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))
total = total / len(numbers)

def get_average(student):

homework = average(student["homework"])
quizzes = average(student["quizzes"])
tests = average(student["tests"])
score = 0.1 * homework + 0.3 * quizzes + 0.6 * tests
print 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(students):
results = []
for student in students:
get_average(student)
results.append(get_average(student))
return average(results)``````

Part of a Whole
#2

lets add a function call so we can see the interpreter error:

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

hm... somehow our `results` list contains None, rather then alice her grade, lets look at get_average why this happened:

``````def get_average(student):

homework = average(student["homework"])
quizzes = average(student["quizzes"])
tests = average(student["tests"])
score = 0.1 * homework + 0.3 * quizzes + 0.6 * tests
print score``````

no `return` keyword in get_average, so the score isn't returned. By default function returns None, which is now being appended to list, this is not what we want in our list

#3

Thank you very much!
Everything is working

#4