Question

I can do it with .txt files, that when something is happening it writes “ok”, and an other program reads it and do something if the .txt file has “ok” inside it. But, I would like to know if I can do with another way.

Answer 1

You could use a signal, e.g. USR1, but I don’t think you can raise signals in Python.
Instead of communicating via a file as you do now you can use a named pipe. A named pipe will provide some extra functionality, see last paragraph.

You open the pipe as an ordinary file and then write and read as you do now. You create the pipe by mkfifo filename, can also be created in your python program. Two example programs for demo:

Sender:

fdw= os.open("./mypipe", os.O_WRONLY)
while (1):
 try:
    os.write(fdw, "OK\n")
 except OSError, e:
    if e.errno==errno.EPIPE:
        #Receiver closed the pipe                                                   
        print "Reader closed pipe\n"
        sys.exit(0)
    else:
        #some other os problem                                                         
        print os.strerror(e.errno)
  time.sleep(3)

Receiver:

fdr= os.open("./mypipe", os.O_RDONLY | os.O_NONBLOCK)
while (1):
  try:
    s= os.read(fdr, 10)
    print s
  except OSError, e:
    if e.errno==errno.EBUSY:
        print "nothing to read yet\n"
    else:
        print os.strerror(e.errno)
  time.sleep(1)

The sender opens a blocking pipe, so you will get an exception if the receiver closes the pipe, usually while terminating. The reader opens a non-blocking pipe so it will not hang while waiting for anything written by the sender. Combinations of blocking/non-blocking yield different responses when sender or receiver close one pipe end. You may want to open the write end non-blocking if there are any chance of pipe overflow (kbytes written, nothing read).