Grep and Python

Question

I need a way of searching a file using grep via a regular expression from the Unix command line. For example when I type in the command line:

python pythonfi         


        

Answer 1

The natural question is why not just use grep?! But assuming you can't...

import re
import sys

file = open(sys.argv[2], "r")

for line in file:
     if re.search(sys.argv[1], line):
         print line,

Things to note:

• search instead of match to find anywhere in string
• comma (,) after print removes carriage return (line will have one)
• argv includes python file name, so variables need to start at 1

This doesn't handle multiple arguments (like grep does) or expand wildcards (like the Unix shell would). If you wanted this functionality you could get it using the following:

import re
import sys
import glob

for arg in sys.argv[2:]:
    for file in glob.iglob(arg):
        for line in open(file, 'r'):
            if re.search(sys.argv[1], line):
                print line,