code: def gen_listfiles(ext, data_path=current_path, start_date=None, end_date=None):
      
      # make list of all files in data directory with certain extension ext
      listfiles = [fn for fn in os.listdir(data_path) if (fn.endswith(ext))]
      # check if start_date & end_date are set
      if (start_date is not None) or (end_date is not None):
          all_dates = pd.date_range(start_date, end_date, freq='D')
          # make list with files in selected range
          files = []
          for date in all_dates:
              yyyy = str(date.year)
              mm = "%02d" % (date.month,)
              dd = "%02d" % (date.day,)
              file = 'A'+yyyy+mm+dd+ext
              files.append(file)
          # compare and return matches
          listfiles = set(listfiles).intersection(files)
          return files
      # if start and end dates aren't set use all files in data dir
      else:
          return listfiles
docs: **Generate list of files in data directory**
  
      Using a specified data path and extension generate list of files in data
      directory. If start_date and end_date aren't specified, all files in the
      data directory are selected.
  
      :paramter data_path: string
      :parameter ext: string
      :parameter start_date: time string in format mm-dd-yyy (optional)
      :paramater end_date: time string in format mm-dd-yyy (optional)
  
      :Example:
  
      >>> gen_listfiles(data_path='./data', ext='.loc', start_date='01-01-2016',
      end_date='01-10-2016')