Python高效查找指定子文件夹：优化大规模目录扫描性能

import os
import re

def find_subfolders_of_interest_legacy(dir_of_interest, starting_string_of_interest):
    """
    使用os.listdir和os.path.isdir查找符合条件的子文件夹（传统方法）。
    """
    all_items = os.listdir(dir_of_interest)
    all_subfolders = []
    for item in all_items:
        full_path = os.path.join(dir_of_interest, item)
        if os.path.isdir(full_path): # 每次调用都会进行系统调用
            all_subfolders.append(item)

    # 使用正则表达式进行名称匹配
    regexp_pattern = re.compile(starting_string_of_interest)
    all_subfolders_of_interest = list(filter(regexp_pattern.match, all_subfolders))
    return all_subfolders_of_interest

# 示例用法
# if __name__ == '__main__':
#     # 假设 'test_folder' 存在且包含子文件夹
#     # all_subfolders_of_interest = find_subfolders_of_interest_legacy('test_folder', 'string_of_interest')
#     # print(all_subfolders_of_interest)

import os

def find_subfolders_of_interest_optimized(dir_of_interest, starting_string_of_interest):
    """
    使用os.scandir高效查找符合条件的子文件夹。
    """
    all_subfolders_of_interest = []

    # os.scandir返回一个迭代器，生成DirEntry对象
    with os.scandir(dir_of_interest) as entries:
        for entry in entries:
            # entry.is_dir()直接使用缓存信息，无需额外系统调用
            # entry.name是目录项的名称
            if entry.is_dir() and entry.name.startswith(starting_string_of_interest):
                all_subfolders_of_interest.append(entry.name)

    return all_subfolders_of_interest

# 示例用法
if __name__ == '__main__':
    # 创建一个测试目录结构
    test_dir = 'large_test_folder'
    if not os.path.exists(test_dir):
        os.makedirs(test_dir)
        # 创建一些测试子文件夹
        for i in range(5):
            os.makedirs(os.path.join(test_dir, f'important_folder_{i}'))
        for i in range(5):
            os.makedirs(os.path.join(test_dir, f'other_folder_{i}'))
        with open(os.path.join(test_dir, 'test_file.txt'), 'w') as f:
            f.write('hello')

    print(f"在 '{test_dir}' 中查找以 'important_folder' 开头的子文件夹...")
    found_folders = find_subfolders_of_interest_optimized(test_dir, 'important_folder')
    print("找到的子文件夹:", found_folders)

    # 清理测试目录 (可选)
    # import shutil
    # if os.path.exists(test_dir):
    #     shutil.rmtree(test_dir)