编写一个带缓存的对文本文件进行读写操作的程序。要求可以读取不同位置的信息，可以爸数据写入到不同的位置。创建一个学生类（含姓名，性别，年龄），从键盘输入学生信息，把学生对象保存在指定文本文件中的指定位置。从文本文件中读取特定学生信息。实现学生信息的增加，删除，修改和插入

以下是一个简单的带缓存的文本文件读写程序的示例：

class FileCache:
    def __init__(self, filename, block_size=1024):
        self.filename = filename
        self.block_size = block_size
        self.cache = {}

    def read(self, pos, size):
        block_start = pos // self.block_size * self.block_size
        block_end = (pos + size - 1) // self.block_size * self.block_size
        data = b""
        for block_pos in range(block_start, block_end + 1, self.block_size):
            if block_pos in self.cache:
                block_data = self.cache[block_pos]
            else:
                with open(self.filename, "rb") as f:
                    f.seek(block_pos)
                    block_data = f.read(self.block_size)
                self.cache[block_pos] = block_data
            data += block_data[pos - block_pos : pos - block_pos + size]
        return data

    def write(self, pos, data):
        block_start = pos // self.block_size * self.block_size
        block_end = (pos + len(data) - 1) // self.block_size * self.block_size
        for block_pos in range(block_start, block_end + 1, self.block_size):
            block_data = self.cache.get(block_pos, b"\x00" * self.block_size)
            block_data = block_data[: pos - block_pos] + data[: self.block_size - (pos - block_pos)] + block_data[
                pos - block_pos + len(data) :
            ]
            self.cache[block_pos] = block_data
            with open(self.filename, "r+b") as f:
                f.seek(block_pos)
                f.write(block_data)
            data = data[self.block_size - (pos - block_pos) :]

class Student:
    def __init__(self, name, gender, age):
        self.name = name
        self.gender = gender
        self.age = age

    def serialize(self):
        return f"{self.name},{self.gender},{self.age}\n".encode()

    @staticmethod
    def deserialize(data):
        name, gender, age = data.decode().strip().split(",")
        return Student(name, gender, int(age))

class StudentDB:
    def __init__(self, filename):
        self.filename = filename
        self.cache = FileCache(filename)

    def add_student(self, student):
        pos = self.cache.write(len(self.cache.read(0, 0)), student.serialize())
        return pos

    def get_student(self, pos):
        data = self.cache.read(pos, 1024)
        return Student.deserialize(data)

    def delete_student(self, pos):
        data = self.cache.read(pos, 1024)
        student = Student.deserialize(data)
        self.cache.write(pos, b"\x00" * len(data))
        return student

    def update_student(self, pos, student):
        data = student.serialize()
        self.cache.write(pos, data)

    def insert_student(self, pos, student):
        data = self.cache.read(pos, 1024)
        self.cache.write(pos + len(data), data)
        self.cache.write(pos, student.serialize())

使用示例：

db = StudentDB("students.txt")

# 添加学生
s1 = Student("张三", "男", 18)
s1_pos = db.add_student(s1)

# 获取学生
s2 = db.get_student(s1_pos)
print(s2.name, s2.gender, s2.age)

# 修改学生
s1.age = 19
db.update_student(s1_pos, s1)
s2 = db.get_student(s1_pos)
print(s2.name, s2.gender, s2.age)

# 插入学生
s3 = Student("李四", "女", 20)
s3_pos = db.add_student(s3)
db.insert_student(s1_pos, s3)
s2 = db.get_student(s1_pos)
print(s2.name, s2.gender, s2.age)
s4 = db.get_student(s3_pos)
print(s4.name, s4.gender, s4.age)

# 删除学生
db.delete_student(s1_pos)