实现按照序号命名的txt文件由后往前递补重命名文件

实现按照序号的命名的txt文件由后往前递补重命名文件
例如现拥有四个文件：

A_1.txt A_3.txt A_4.txt A_5.txt

实现变成A_1.txt~A_4.txt

3->2 4->3 5->4

import pathlib
import os


def fill_sequence(input_path, keywords_list):
    for kw in keywords_list:
        print(f'Fill sequence {
      enu + 1}/{
      (len(keywords_list))} keyword:', kw)
        txtdir_path = input_path + '/' + kw
        all_txt_file = list(pathlib.Path(txtdir_path).glob('**/*.txt'))
        for i in range(len(all_txt_file)):
            input_file = txtdir_path + f'/{
      kw}_{
      i + 1}.txt'
            # input_filename = f'{kw}_{i + 1}.txt'
            if not os.path.exists(input_file):
                for add in range(2, 50):
                    next_file = txtdir_path + f'/{
      kw}_{
      i + add}.txt'
                    # next_filename = f'{kw}_{i + add}.txt'
                    if os.path.exists(next_file):
                        os.rename(next_file, input_file)
                        break


if __name__ == '__main__':
    input_path = ""
    keywords_list = ['A', 'B', 'C']
    fill_sequence(input_path, keywords_list)