1.建立一张学生成绩表，每个学生包含 学号、姓名、性别、语文、数学、英语、总分、平均分。 2.将表中所有信息按总分降序排列。 3.按学号查找某学生所有成绩。 4.能够实现某学生的成绩插入和删除。 5.实现文件操作，程序退出时将学生成绩保存在studen_grad.txt文件中；程序开始时，能够从student_grad.txt文件中加载已有的学生成绩信息。

好的，这个问题可以用Python语言来实现。我们可以定义一个类`Student`来表示学生信息，然后再定义一个类`GradeTable`来表示学生成绩表。下面是代码实现：

import os

class Student:
    def __init__(self, id, name, gender, chinese, math, english):
        self.id = id
        self.name = name
        self.gender = gender
        self.chinese = chinese
        self.math = math
        self.english = english
        self.total_score = chinese + math + english
        self.average_score = round(self.total_score / 3, 2)

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

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

    def remove_student(self, id):
        for student in self.students:
            if student.id == id:
                self.students.remove(student)
                return True
        return False

    def search_student(self, id):
        for student in self.students:
            if student.id == id:
                return student
        return None

    def sort_by_total_score(self):
        self.students.sort(key=lambda x: x.total_score, reverse=True)

    def save_to_file(self, filename):
        with open(filename, 'w') as f:
            for student in self.students:
                f.write(f"{student.id},{student.name},{student.gender},{student.chinese},{student.math},{student.english}\n")

    def load_from_file(self, filename):
        if os.path.exists(filename):
            with open(filename, 'r') as f:
                for line in f.readlines():
                    data = line.strip().split(',')
                    student = Student(data[0], data[1], data[2], int(data[3]), int(data[4]), int(data[5]))
                    self.add_student(student)

if __name__ == '__main__':
    grade_table = GradeTable()
    grade_table.load_from_file('student_grad.txt')
    while True:
        print("1.添加学生")
        print("2.删除学生")
        print("3.查找学生")
        print("4.显示成绩排名")
        print("5.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：")
            gender = input("请输入性别：")
            chinese = int(input("请输入语文成绩："))
            math = int(input("请输入数学成绩："))
            english = int(input("请输入英语成绩："))
            student = Student(id, name, gender, chinese, math, english)
            grade_table.add_student(student)
            print("添加成功！")
        elif choice == '2':
            id = input("请输入学号：")
            if grade_table.remove_student(id):
                print("删除成功！")
            else:
                print("学号不存在！")
        elif choice == '3':
            id = input("请输入学号：")
            student = grade_table.search_student(id)
            if student:
                print(f"学号：{student.id}，姓名：{student.name}，性别：{student.gender}，语文：{student.chinese}，数学：{student.math}，英语：{student.english}，总分：{student.total_score}，平均分：{student.average_score}")
            else:
                print("学号不存在！")
        elif choice == '4':
            grade_table.sort_by_total_score()
            for i, student in enumerate(grade_table.students):
                print(f"{i+1} 学号：{student.id}，姓名：{student.name}，总分：{student.total_score}")
        elif choice == '5':
            grade_table.save_to_file('student_grad.txt')
            print("学生成绩已保存到文件！")
            break
        else:
            print("输入错误，请重新输入！")

你可以将上述代码保存为一个Python文件，比如`grade_system.py`，然后在命令行中运行`python grade_system.py`来启动程序。