Creating random time stamps and saving it in a file

from random import randrange
import datetime
import numpy as np

def random_date(start,l):
   current = start
   while l >= 0:
      curr = current + datetime.timedelta(minutes=randrange(60))
      yield curr
      l-=1

startDate = datetime.datetime(2013, 9, 20,13,00)
f = open('filepath name\filename.txt','w')
for x in random_date(startDate,500):
    f.write((x.strftime(""%d/%m/%y"","" %H:%M,")))
f.close()