regex - filter a Linux log file using Python -

i want filter log file keep lines matching pattern. want python.

here's first attempt:

#!/usr/bin/env python  sys import argv   script, filename = argv open(filename) f:     line in f:         try:             e = line.index("some_term_i_want_to_match")         except:              pass         else:             print(line) 

how can improve to:

• save result new file of similar name (i.e., different extension)
• use regex make more flexible/powerful.

(i'm learning python. question learning python accomplishing particular result.)

ok, here's came far... how do equivalent of prepending r in following line

re.compile(r"\s*") 

where string not string literal, in next line?

re.compile(a_string_variable) 

other that, think updated version job:

#!/usr/bin/env python  sys import argv  import re import os import argparse #requires python 2.7 or above  parser = argparse.argumentparser(description='filters text file on search phrase') parser.add_argument('-s','--search', help='search phrase or keyword match',required=true) parser.add_argument('-f','--filename', help='input file name',required=true) parser.add_argument('-v','--verbose', help='display output screen too', required=false, action="store_true") args = parser.parse_args()  keyword = args.search original_file = args.filename verbose = args.verbose  base_file, ext = os.path.splitext(original_file) new_file = base_file + ".filtered" + ext  regex_c = re.compile(keyword)  open(original_file) fi:     open(new_file, 'w') fo:         line in fi:             result = regex_c.search(line)             if(result):                 fo.write(line)                 if(verbose):                     print(line) 

can improved?

well, know, have answered of questions :)

for regular expression matching use re module (the doc has pretty explanatory examples).

you have made use open() function opening file. use same function open files writing, provide corresponding mode parameter ("w" or "a" combined "+" if need, see help(open) in python interactive shell). that's it.