grep.py

#! /usr/bin/env python3
""" grep.py - Search a string in a file. """

import sys


# Parse arguments
pattern, file_name = sys.argv[1:3]

with open(file_name, 'rt') as f:
    for n, line in enumerate(f, 1):
        if pattern in line:
            print('Line %03d:' % n, line, end='')