How to do other stuff while user deciding if write anything in raw_input?

Question

while True:
  mess = raw_input('Type: ')
  //other stuff

While user doesn't type anything, I can't do //other stuff. How can I do, that other stuff would be executed, but, if user types anything at that time, mess would change its value?

Answer 1

You should spawn your other stuff in a worker thread.

import threading
import time
import sys

mess = 'foo'

def other_stuff():
  while True:
    sys.stdout.write('mess == {}\n'.format(mess))
    time.sleep(1)

t = threading.Thread(target=other_stuff)
t.daemon=True
t.start()

while True:
  mess = raw_input('Type: ')

This is a trivial example with mess as a global. Note that for thread-safe passing of objects between worker thread and main thread, you should use a Queue object to pass things between threads, don't use a global.

Answer 2

As an alternative to using a worker thread you could poll whether the user input is available on Unix via select.select():

import select
import sys

def raw_input_timeout(prompt=None, timeout=None):
    if prompt is not None:
        sys.stdout.write(prompt)
        sys.stdout.flush()
    ready = select.select([sys.stdin], [],[], timeout)[0]
    if ready:
        # there is something to read
        return sys.stdin.readline().rstrip('\n')

prompt = "First value: "
while True:
    s = raw_input_timeout(prompt, timeout=0)
    if s is not None:
        mess = s # change value
        print(repr(mess))
        prompt = "Type: " # show another prompt
    else:
        prompt = None # hide prompt
    # do other stuff

Each time the user presses Enter the mess value is changed.