用Python语言编写班级成绩统计分析系统软件，完成以下任务：记录学生成绩信息，学生成绩信息结构至少应该包括以下几项：学号、姓名、班级、数学成绩、英语成绩。主要功能包括： 系统的界面菜单； 学生成绩信息输入； (3) 统计每个班级的人数； (4) 分别统计每个班级的数学、英语平均分； (5) 将学生成绩信息按班级存在不同的文本文件（.txt）中，文件名称为“班级名称.txt”，文件中按学生学号排序； (6) 退出程序。

这是一个很好的问题，我为你提供以下参考代码：

import os

class Student:
    def __init__(self, id, name, cls, math_score, eng_score):
        self.id = id
        self.name = name
        self.cls = cls
        self.math_score = math_score
        self.eng_score = eng_score

class GradeAnalyzer:
    def __init__(self):
        self.students = []

    def add_student(self, student):
        self.students.append(student)

    def get_class_count(self, cls):
        count = 0
        for student in self.students:
            if student.cls == cls:
                count += 1
        return count

    def get_class_avg_score(self, cls, subject):
        total_score = 0
        count = 0
        for student in self.students:
            if student.cls == cls:
                if subject == "math":
                    total_score += student.math_score
                elif subject == "eng":
                    total_score += student.eng_score
                count += 1
        if count == 0:
            return 0
        else:
            return total_score / count

    def save_to_file(self):
        classes = set([student.cls for student in self.students])
        for cls in classes:
            students = [student for student in self.students if student.cls == cls]
            students.sort(key=lambda student: student.id)
            filename = cls + ".txt"
            with open(filename, "w") as f:
                f.write("学号\t姓名\t班级\t数学成绩\t英语成绩\n")
                for student in students:
                    f.write("{}\t{}\t{}\t{}\t{}\n".format(student.id, student.name, student.cls, student.math_score, student.eng_score))

if __name__ == "__main__":
    analyzer = GradeAnalyzer()
    while True:
        print("1. 添加学生信息")
        print("2. 统计班级人数")
        print("3. 统计班级数学平均分")
        print("4. 统计班级英语平均分")
        print("5. 将学生成绩信息按班级存在不同的文本文件中")
        print("6. 退出程序")
        choice = input("请选择操作：")
        if choice == "1":
            id = input("请输入学号：")
            name = input("请输入姓名：")
            cls = input("请输入班级：")
            math_score = int(input("请输入数学成绩："))
            eng_score = int(input("请输入英语成绩："))
            student = Student(id, name, cls, math_score, eng_score)
            analyzer.add_student(student)
        elif choice == "2":
            cls = input("请输入班级：")
            count = analyzer.get_class_count(cls)
            print("班级人数为：{}".format(count))
        elif choice == "3":
            cls = input("请输入班级：")
            avg_score = analyzer.get_class_avg_score(cls, "math")
            print("班级数学平均分为：{}".format(avg_score))
        elif choice == "4":
            cls = input("请输入班级：")
            avg_score = analyzer.get_class_avg_score(cls, "eng")
            print("班级英语平均分为：{}".format(avg_score))
        elif choice == "5":
            analyzer.save_to_file()
            print("学生成绩信息已保存到文件中")
        elif choice == "6":
            print("程序已退出")
            break
        else:
            print("无效的选项，请重新选择")