just weight and see | Python Fiddle

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!

def average(li):
    #Durchschnitt ermitteln
    return float(sum(li))/len(li)
    
def get_average(nli):
    #Durchschnitt in Listen zu vorgegebenen Prozentsatz ermitteln 
    return average(nli['homework'])*0.1 + average(nli['quizzes'])*0.3 + average(nli['tests'])*0.6

def get_letter_grade(score):
    #Berechnung der Note anhand der Ergebnisse aus einer Funktion
    if score >= 90:
        return 'A'
    if score >= 80 and score < 90:
        return 'B'
    if score >= 70 and score < 80:
        return 'C'
    if score >= 60 and score < 70:
        return 'D'
    if score < 60:
        return 'F'
        
        
#ausführen der Funktion zur errechnung der Note anhand des ergebnisses aus get_average()

print get_letter_grade(get_average(lloyd))

students = [lloyd,alice,tyler]

def get_class_average(stud):
    #durchschnittsnote errechnet aus einer Liste mit Schülern
    summary = 0
    for x in stud:
        #print x
        summary += float(get_average(x))
    ende = summary/len(stud)
    return ende
    
print get_class_average(students)

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