import osdirPath = '.'def problem2(path, key=None):    try:        for x in os.listdir(path):  # 列出所有文件或文件夹            if os.path.isdir(x):  # 是目录                problem2(os.path.join(path, x), key)            else:  # 是文件                if key:  # 有关键字                    if key in x:  # 打印出含关键字的路径                        print(os.path.join(path, x))                else:  # 无关键字，则全部显示                    print(os.path.join(path, x))    except Exception as e:        raise eproblem2(dirPath, '.py')