如何向未知扩展名文件添加扩展名

import os

def add_extension(file_path, extension):
    # 获取文件名和文件所在的目录
    file_name = os.path.basename(file_path)
    directory = os.path.dirname(file_path)
    
    # 将扩展名添加到文件名中
    new_file_name = file_name + extension
    
    # 构建新的文件路径
    new_file_path = os.path.join(directory, new_file_name)
    
    # 重命名文件
    os.rename(file_path, new_file_path)

# 示例用法
file_path = "path/to/unknown_file"
extension = ".txt"
add_extension(file_path, extension)