自动化下载如何处理断点续传？

python复制import os
import requests

def download_file(url, local_filename):
    # 检查已下载的文件大小
    if os.path.exists(local_filename):
        resume_header = {'Range': f'bytes={os.path.getsize(local_filename)}-'}
    else:
        resume_header = {}

    # 发送请求
    response = requests.get(url, headers=resume_header, stream=True)

    # 检查响应状态
    if response.status_code not in (200, 206):
        print(f"Error: {response.status_code}")
        return

    # 以追加模式打开文件
    with open(local_filename, 'ab') as f:
        for chunk in response.iter_content(chunk_size=8192):
            f.write(chunk)

    print(f"Downloaded: {local_filename}")

if __name__ == "__main__":
    url = "http://example.com/largefile.zip"
    local_filename = "largefile.zip"
    download_file(url, local_filename)