Show file and filter by keyword like cat and grep.

cat_grep.py

import sys 
import os
def main(args):
  directory = args[1]
  if len(args) > 2:
    keyword = args[2]
  else:
    keyword = ''

  file_list = os.listdir(directory)
  for item in file_list:
    if os.path.isfile(item) and 'py' in item:
      for line in open(item):
        if keyword == '' or keyword in line:
          print(str(item) + ' ', end='')
          print(line, end='')

if __name__ == '__main__':
  main(sys.argv)