面向对象用python写出可断点下载的代码

下面是一个简单的面向对象的 Python 下载器，可以实现断点续传的功能：

import requests


class Downloader:
    def __init__(self, url, chunk_size=1024):
        self.url = url
        self.chunk_size = chunk_size
        self.file_size = int(requests.head(url).headers.get('Content-Length', 0))
        self.file_name = url.split('/')[-1]
        self.completed = False

    def start(self):
        headers = {"Range": f"bytes=0-{self.chunk_size}"}
        response = requests.get(self.url, headers=headers, stream=True)

        with open(self.file_name, 'wb') as f:
            f.write(response.content)

        while not self.completed:
            self.resume()

    def resume(self):
        headers = {"Range": f"bytes={os.path.getsize(self.file_name)}-{self.file_size}"}
        response = requests.get(self.url, headers=headers, stream=True)

        with open(self.file_name, 'ab') as f:
            for chunk in response.iter_content(chunk_size=self.chunk_size):
                if chunk:
                    f.write(chunk)

            if os.path.getsize(self.file_name) == self.file_size:
                self.completed = True

使用方法：

downloader = Downloader('https://example.com/large_file.zip')
downloader.start()

这个下载器会在开始时先下载前 1KB 的数据，然后再按照文件大小分块下载，直到下载完成。如果下载过程中中断，再次运行下载器会自动从上次中断的位置继续下载。