grep made bad in python

grep.py

import sys
import re

pattern = re.compile(sys.argv[1])
last = int(len(sys.argv)) - 1
reverse = True if sys.argv[last] == '-v' else False
lines = sys.stdin.readlines()
for line in lines:
	if bool(pattern.search(line)) != reverse:
		sys.stdout.write(line)

w..why?

(also, why not ack?)

You can just do:
reverse = sys.argv[last] == '-v'
Instead of the if/else.