使用一个文件虚拟一个含分页式虚拟内存，并且使用lru算法的的文件系统的python代码

以下是一个简单的使用 LRU 算法模拟分页式虚拟内存的 Python 代码：

import os

class Page:
    def __init__(self, page_num, data=None):
        self.page_num = page_num
        self.data = data

class Disk:
    def __init__(self, filename):
        self.filename = filename
        self.pages = {}
        if os.path.isfile(filename):
            with open(filename, 'rb') as f:
                while True:
                    page_num_bytes = f.read(4)
                    if not page_num_bytes:
                        break
                    page_num = int.from_bytes(page_num_bytes, 'big')
                    page_data = f.read(4096)
                    self.pages[page_num] = Page(page_num, page_data)

    def read_page(self, page_num):
        if page_num in self.pages:
            # page is already in memory, return it
            return self.pages[page_num].data
        else:
            # page is not in memory, load it from disk
            with open(self.filename, 'rb') as f:
                f.seek(page_num * 4096)
                page_data = f.read(4096)
            self.pages[page_num] = Page(page_num, page_data)
            return page_data

    def write_page(self, page_num, page_data):
        with open(self.filename, 'r+b') as f:
            f.seek(page_num * 4096)
            f.write(page_data)
        self.pages[page_num] = Page(page_num, page_data)

    def flush(self):
        with open(self.filename, 'wb') as f:
            for page in sorted(self.pages.values(), key=lambda p: p.page_num):
                f.write(page.page_num.to_bytes(4, 'big'))
                f.write(page.data)

class PageTable:
    def __init__(self, disk):
        self.disk = disk
        self.pages = {}
        self.lru_queue = []

    def read_page(self, page_num):
        if page_num in self.pages:
            # move page to front of LRU queue
            self.lru_queue.remove(page_num)
            self.lru_queue.insert(0, page_num)
            return self.pages[page_num]
        else:
            # page is not in memory, load it from disk
            page_data = self.disk.read_page(page_num)
            if len(self.pages) >= 10:
                # remove least recently used page from memory
                lru_page_num = self.lru_queue.pop()
                del self.pages[lru_page_num]
            self.pages[page_num] = page_data
            self.lru_queue.insert(0, page_num)
            return page_data

    def write_page(self, page_num, page_data):
        if page_num in self.pages:
            # move page to front of LRU queue
            self.lru_queue.remove(page_num)
            self.lru_queue.insert(0, page_num)
        else:
            if len(self.pages) >= 10:
                # remove least recently used page from memory
                lru_page_num = self.lru_queue.pop()
                del self.pages[lru_page_num]
            self.lru_queue.insert(0, page_num)
        self.pages[page_num] = page_data
        self.disk.write_page(page_num, page_data)

    def flush(self):
        self.disk.flush()

# example usage:

disk = Disk('virtual_memory.bin')
page_table = PageTable(disk)

# read page 0
page_data = page_table.read_page(0)
print(page_data)

# write to page 1
page_table.write_page(1, b'hello world')

# read page 1
page_data = page_table.read_page(1)
print(page_data)

# flush changes to disk
page_table.flush()

此代码模拟了一个包含 10 个页面的虚拟内存，每个页面大小为 4096 字节。使用 LRU 算法来管理页面，如果有新页面需要加载到内存中，将会淘汰最近最少使用的页面。Disk 类用于模拟磁盘，PageTable 类用于管理内存中的页面和磁盘中的页面。请注意，此代码仅作为示例，不适用于生产环境。