列表中字典中的Python列表-引用时不带整数（字符串？）

Question

This question problem is from code academy. I have come up with a solution although not quite satisfied, as I think I am programmatically cheating to make code work. Are there other ways to solve this. I have seen harder code. This one is fairly straight forward.

Three dictionaries on students that have four keys. Three of the keys are lists. function to calculate average function to calculate letter grade function to calculate average on each kid

Okay thing is, calling the average on each kid function to calculate the average works fine as do all the functions.

However, if a new list is create to include all 3 students --- that makes student list, with 3 list items. Each item has a dictionary, with four keys. Three of the four keys are lists. Phew!!!

I have used a for loop with a counter and an increment in the getClassAverage function to calculate average.

Questions:

• Is there another way to calculate average without a for loop ie just within the function as just using "who" passed argument makes it have the students (data) and does not reference well with the list. Gives indexing with string, not integer" error?

• With list inside key, inside list. How will I print a student name from the getClassAverage function?

Thanks!

Lloyd = {
    "name":"Lloyd",
    "homework": [90,97,75,92],
    "quizzes": [ 88,40,94],
    "tests": [ 75,90]
    }
Alice = {
    "name":"Alice",
    "homework": [100,92,98,100],
    "quizzes": [82,83,91],
    "tests": [89,97]
    }
Tyler = {
    "name":"Tyler",
    "homework": [0,87,75,22],
    "quizzes": [0,75,78],
    "tests": [100,100]
    }

def average(stuff):
    return sum(stuff)/len(stuff)

def getLetterGrade(score):
    score = round(score)
    if  score >= 90: return "A"
    elif  90 > score >= 80: return "B"
    elif  80 > score >= 70: return "C"
    elif  70 > score >= 60: return "D"
    elif  60 > score: return "F"

def getAverage(kid):
    bar = average
    return bar(kid["homework"])*.1 + bar(kid["quizzes"])*.3 + bar(kid["tests"])*.6

students = [Lloyd,Alice,Tyler]

def getClassAverage(who):
    class_ave = 0
    class_avetot = 0
    count = 0
    for x in who:
        class_avetot = class_avetot + getAverage(who[count])
        #print who[count]
        stu_score = getAverage(who[count])
        print stu_score
        print getLetterGrade(stu_score)
        count = count + 1
    class_ave = class_avetot / len(who)
    return class_ave

print str(getClassAverage(students))

Answer 1

To estimate average, numpy has a function that you can use.

from numpy import average

In getClassAverage function you are passing a list with the names of the students. So if you do:

for x in who:
        print x  # This prints the name of the student
        class_avetot = class_avetot + getAverage(who[count])

It will print the name of the student as you estimate his average grade to add to the class average.

Hope that helps.

Answer 2

Using your code and functions you already have, try this:

def getClassAverage (who):
    return average ( [getAverage (kid) for kid in who] )

Your code is fine. I will just post how I would have possibly implemented this to give you another point of few, and not to say that my version be better or nicer:

#! /usr/bin/python3.2

def ave (x): return sum (x) / len (x)

def getLetterGrade (score):
    score = round (score)
    if score >= 90: return 'A'
    if score >= 80: return 'B'
    if score >= 70: return 'C'
    if score >= 60: return 'D'
    #Why no grade E?
    return 'F'

class Student:
    def __init__ (self, name, homework, quizzes, tests):
        self.name = name
        self.homework = homework
        self.quizzes = quizzes
        self.tests = tests

    @property
    def average (self):
        return ave (self.homework) * .1 + ave (self.quizzes) * .3 + ave (self.tests) * .6

    def printAverage (self):
        print ('{} has an average of {:.2f} ({})'.format (self.name, self.average, getLetterGrade (self.average) ) )

class Class:
    def __init__ (self, students):
        self.students = students

    @property
    def average (self):
        return ave ( [student.average for student in self.students] )

    def printStudents (self):
        for student in students:
            student.printAverage ()

    def printAverage (self):
        print ('The class has an average of {:.2f}'.format (self.average) )

students = [Student ('Lloyd', [90,97,75,92], [88,40,94], [75,90] ),
    Student ('Alice', [100,92,98,100], [82,83,91], [89,97] ),
    Student ('Tyler', [0,87,75,22], [0,75,78], [100,100] ) ]

myClass = Class (students)
myClass.printStudents ()
myClass.printAverage ()

(Inb4 PEP8, I know it, I have read it, I choose to ignore it.)