Removing unnecessary lines from file v2

# -*- coding: utf-8 -*-
import os.path
import time
import re

def getRegex():
    regex = ''
    with open(file_with_urls, 'r') as body:
        for line in body:
            regex += line.strip('\n') + '|'
    return re.compile(regex[:-1])

def prepareHosts(regex):
    with open(file_to_open, 'r', encoding='utf8') as content:
        with open(file_to_save, 'a', encoding='utf8') as file_:
            for line in content:
                if not regex.search(line):
                    file_.write(line)

getTime = lambda: int(round(time.time() * 1000))
start = getTime()

file_to_save = 'cleared_hosts'
file_to_open = 'hosts'
file_with_urls = 'urls_list.txt'

if os.path.isfile(file_to_save):
    os.remove(file_to_save)

prepareHosts(getRegex())
print("Took {0}ms".format(getTime() - start))