#!/usr/bin/python

# A calculator for grades, student scores are stored in dictionaries
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]
}


# Gets float average of argument
def average(numbers):
    total = sum(numbers)
    total = float(total)
    return total/len(numbers)


# Returns weighted average of student grade.
# Homework = 10%, Quizzes = 30%, Tests = 60%
def get_average(student):
    homework = average(student["homework"])
    quizzes = average(student["quizzes"])
    tests = average(student['tests'])
    return 0.1*homework + 0.3*quizzes + 0.6*tests


# Returns letter grade
def get_letter_grade(score):
    if score >= 90.:
        return "A"
    elif score < 90. and score >= 80.:
        return "B"
    elif score < 80 and score >= 70.:
        return "C"
    elif score < 70 and score >= 60:
        return "D"
    else:
        return "F"


# Calculates class average and returns result
def get_class_average(class_list):
    results = []
    for student in class_list:
        results.append(get_average(student))
    return average(results)


# Prints the letter grade of Lloyd's weighted average number grade
print get_letter_grade(get_average(lloyd))

# Gets class average and prints to the console
students = [alice, lloyd, tyler]
print get_class_average(students)
