Question

I have a thread which can print some text on the console and the main program have a raw_input to control the thread.

My problem is when I’m writing and the thread too I get something like this:

-->whatiwWHATTHETHREADWRITErite

but I would like to get some thing like this

WHATTHETHREADWRITE
-->whatiwrite

Answer 1

You have to syncronize your input with the thread output preventing them from happening at the same time.

You can modify the main loop like:

lock = threading.lock()

while 1:
    raw_input()     # Waiting for you to press Enter
    with lock:
        r = raw_input('--> ')
        # send your command to the thread

And then lock the background thread printing:

def worker(lock, ...):
    [...]
    with lock:
        print('what the thread write')

In short when you Press Enter you will stop the thread and enter in “input mode”.

To be more specific, every time you Press Enter you will:

• wait for the lock to be available
• acquire the lock
• print --> and wait for your command
• insert your command
• send that command to the thread
• release the lock

So your thread will be stopped only if it tries to print when you are in “input mode”,
and in your terminal you’ll get something like:

some previous output

---> your input
THE THREAD OUTPUT