Autochecker

import re, subprocess, random, time, os, sys

def openFile(fname):
   f = open(fname)
   input = f.read()
   f.close()
   return re.sub('[^a-zA-Z .,?!]+', '', input)

def generateString(input):
   startChar = random.randint(1, len(input)-170)
   return input[startChar:startChar+random.randint(0,160)]

def testString(str):
   f = open("input.txt", "wb")
   f.write(str)
   f.close()
   print("Testing string:" + str)
   cout = subprocess.check_output("./a.out",shell=True)
   mipsout = subprocess.check_output("java -jar Mars.jar sm nc punctuation_checker.s",shell=True)
   if (mipsout[-1:] == '\n'):
      mipsout = mipsout[:-1] #trailing newline on MARS output
   if mipsout == cout:
      print "Passed."
      print ""
   else:
      print "FAILED"
      sys.exit("stopped due to mismatch between C and MIPS output")

f = openFile(sys.argv[1])
while 1:
   str = generateString(f)
   testString(str)