class SimpleGradebook():

    def __init__(self):

        self.__grades = {}

    def add_student(self, name):

        self.__grades[name] = []    # 一个学生对应一个成绩列表

    def report_grade(self, name, score):

        self.__grades[name].append(score)

    def average_grade(self, name):

        grades = self.__grades[name]

        return sum(grades) / len(grades)    # 计算一个学生的平均成绩

book = SimpleGradebook()

book.add_student('ss')

book.report_grade('ss', 90)

book.report_grade('ss', 100)

print(book.average_grade('ss'))

class SimpleGradebook():

    def __init__(self):

        self.__grades = {}

    def add_student(self, name):

        self.__grades[name] = {}    # 一个学生的成绩加入科目分类，所以用字典存储

    def report_grade(self, name, subject, score):

        by_subject = self.__grades[name]

        grade_list = by_subject.setdefault(subject, [])     # 存在该科目则返回已有列表，不存在则返回一个空列表

        grade_list.append(score)

    def average_grade(self, name):

        by_subject = self.__grades[name]

        total, count = 0, 0

        for grades in by_subject.values():

            total += sum(grades)

            count += len(grades)

        return total / count

book = SimpleGradebook()

book.add_student('ss')

book.report_grade('ss', 'Math', 90)

book.report_grade('ss', 'Math', 100)

print(book.average_grade('ss'))

from collections import namedtuple, defaultdict

Grade = namedtuple('Grade', ('score', 'weight'))    # 具名元组

class Subject:

    # 科目的类，包含成绩和权重

    def __init__(self):

        self._grades = []

    def report_grade(self, score, weight):

        self._grades.append(Grade(score, weight))

    def average_grade(self):

        total, total_weight = 0, 0

        for grade in self._grades:

            total += grade.score * grade.weight

            total_weight += grade.weight

        return total / total_weight

class Student:

    # 学生的类，包含各项课程

    def __init__(self):

        self._subjects = defaultdict(Subject)

    def get_subject(self, name):

        return self._subjects[name]

    def average_grade(self):

        total, count = 0, 0

        for subject in self._subjects.values():

            total += subject.average_grade()

            count += 1

        return total / count

class Gradebook:

    # 所有学生成绩的容器类，以学生的名字为键

    def __init__(self):

        self._students = defaultdict(Student)

    def get_student(self, name):

        return self._students[name]

book = Gradebook()

albert = book.get_student('ss')

math = albert.get_subject('Math')

math.report_grade(75, 0.05)

math.report_grade(65, 0.15)

math.report_grade(70, 0.80)

gym = albert.get_subject('Gym')

gym.report_grade(100, 0.40)

gym.report_grade(85, 0.60)

print(albert.average_grade())