Read linux dmesg with date

Simple script to read dmesg from linux (contains real date no miliseconds)
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#!/usr/bin/python
import sys
import re
import time
import datetime
import fileinput
import os

try:
  uptime = open('/proc/uptime','r')
except IOError as (errno, strerror):
  print "Wystapil blad otwarcia pliku :\n %s\n" % (strerror)

czas = time.time()

uptime_seconds = czas-float(uptime.readline().split()[0])

p = os.popen('dmesg')

for line in p.readlines():

  re1='.*?'
  re2='(\\d+)'
  re3='(\\.)'
  re4='(\\d+)'

  rg = re.compile(re1+re2+re3+re4,re.IGNORECASE|re.DOTALL)
  m = rg.search(line)
  if m:
      int1=float(m.group(1)+m.group(2)+m.group(3))
      szukaj=(m.group(1)+m.group(2)+m.group(3))
      czas = uptime_seconds + int1
      czas = datetime.datetime.fromtimestamp(int(czas)).strftime('%Y-%m-%d %H:%M:%S')
   
      zwrot = re.sub(szukaj,czas,line.rstrip(),1)

      print zwrot