python-按指定文件名前缀查找文件并保留n个最新文件

# -*- coding:utf-8 -*-
# 实现自动保留ctime最近的几个文件

import os


def rm_backup(files_list, days):
    """
    删除文件列表中的时间最早的文件
    :param files_list: 文件列表
    :param days:保留天数
    """
    dic = {}
    for i in files_list:
        all_path = i
        ctime = os.path.getctime(all_path)
        dic[all_path] = ctime
    all_path_ctime_list = sorted(dic.items(), key=lambda item: item[1])
    if len(all_path_ctime_list) <= days:
        pass
    else:
        for i in range(len(all_path_ctime_list) - days):
            os.remove(all_path_ctime_list[i][0])


def list_file(prefix, dirs=os.path.abspath('.'), res=None):
    """
    查找当前目录下以prefix为前缀的文件路径列表
    :param prefix: 前缀名
    :param dirs: 查找目录
    :param res: 结果
    :return: 结果
    """
    if res is None:
        res = []
    for x in os.listdir(dirs):
        path = os.path.join(dirs, x)
        if os.path.isfile(path) and os.path.splitext(x)[0].startswith(prefix):
            res.append(path)
        if os.path.isdir(path):
            list_file(prefix, path, res)
    return res


rm_paths = list_file("valid_content")
rm_backup(rm_paths, 3)