Removing unnecessary lines from file

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

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

output_file = 'cleared_hosts' #file where content will be placed
start = getTime()

def getRegex():
    regex = ''
    with open('urls_list.txt', 'r') as body: #file with list of lines to remove
        for line in body:
            regex += line.strip('\n') + '|'
    return re.compile(regex[:-1])

def prepareHosts(regex):
    with open('hosts', 'r') as content: #file we want to remove lines from
        for line in content:
            if not regex.search(line):
                writeToFile(line)

def writeToFile(text):
    with open(output_file, 'a') as file_:
        file_.write(text)


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

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