code: def get_abs_filename_with_sub_path(sub_path, filename):
  
      
  
      try:
          cur_path = pathlib.Path.cwd()
          abs_filename = cur_path / pathlib.Path(sub_path) / filename
          flag = pathlib.Path.is_file(abs_filename)
  
          # 将 path 对象转换成字符串
          return flag, str(abs_filename)
  
      except:
  
          flag = False
          return flag, None
docs: 生成当前路径下一级路径某文件的完整文件名；
  
          :param:
              * sub_path: (string) 下一级的某路径名称
              * filename: (string) 下一级路径的某个文件名
          :returns:
              * 返回类型 (tuple)，有两个值，第一个为 flag，第二个为文件名，说明见下
              * flag: (bool) 如果文件存在，返回 True，文件不存在，返回 False
              * abs_filename: (string) 指定 filename 的包含路径的长文件名
  
          举例如下::
              
              print('--- get_abs_filename_with_sub_path demo ---')
              # define sub dir
              path_name = 'sub_dir'
              # define not exists file
              filename = 'test_file.txt'
  
              abs_filename = get_abs_filename_with_sub_path(path_name, filename)
              # return False and abs filename
              print(abs_filename)
  
              # define exists file
              filename = 'demo.txt'
              abs_filename = get_abs_filename_with_sub_path(path_name, filename)
              # return True and abs filename
              print(abs_filename)
              print('---')
  
          输出结果::
              
              --- get_abs_filename_with_sub_path demo ---
              (False, '/Users/****/Documents/dev_python/fishbase/demo/sub_dir/test_file.txt')
              (True, '/Users/****/Documents/dev_python/fishbase/demo/sub_dir/demo.txt')
              ---