open LPT1, read from it, save changes to a file

gistfile1.py

import ctypes
import time
import datetime

#a bunch of win32 constants; unfortunately must be hardcoded here
GENERIC_READ = 0x80000000
SHARE_NONE = 0
OPEN_EXISTING = 3
FILE_ATTRIBUTE_NONE = 0

handle = ctypes.windll.kernel32.CreateFileA("\\.\LPT1", GENERIC_READ,
            SHARE_NONE, None, OPEN_EXISTING, FILE_ATTRIBUTE_NONE, None)

if handle == -1:
    print "ERROR: unable to open LPT1 port"
    print ctypes.FormatError() #win32 library description of problem

def read(handle):
    buffer = ctypes.create_string_buffer(32)
    amount_read = ctypes.create_string_buffer(2)
    ctypes.windll.kernel32.ReadFile(handle, buffer, 32, amount_read, None)
    return [bin(ord(a)) for s in buffer[:ord(amount_read[0])]]
 
lastval = None
val = None
file = open("parallel_values.txt", "a")

while True: #terminate program with Ctrl-C
    lastval = val
    val = read(handle)
    if val != lastval:
        file.write(str(val)+" "+str(datetime.datetime.now())+"\n")
    time.sleep(0.01) #sleep for 10ms to free CPU