如何在python的变量中复制包含具有特定扩展名的特定文件的目录

import os
import shutil

def copy_files_with_extension(source_dir, target_dir, extension):
    for root, dirs, files in os.walk(source_dir):
        for file in files:
            if file.endswith(extension):
                source_file = os.path.join(root, file)
                target_file = os.path.join(target_dir, file)
                shutil.copy2(source_file, target_file)

source_dir = '/path/to/source/directory'
target_dir = '/path/to/target/directory'
extension = '.txt'

copy_files_with_extension(source_dir, target_dir, extension)