Grep and Python

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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:

#!/usr/bin/env python3

import re
import sys
import glob

regexp = re.compile(sys.argv[1])
for arg in sys.argv[2:]:
    for fn in glob.iglob(arg):
        with open(fn) as file:
            for line in file:
                if re.search(regexp, line):
                    print(line, end='')

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