Python "print" causes threading deadlock

Question

I have a large system with workers and manager threads.

I have run into the problem that one of the threads uses:

print "before time sleep"
time.sleep(5)
print "after time sleep"

It will print both a lot of times and then suddenly only display "before time sleep" And stop until i kill all the other threads. None of the other threads are stopping.

I think some other part of the code is locking the commandline output or something like that, but I have no idea how to find the spot (it can take up to 24 hours before it happens)

I'm using python 2.7 and the error occurs on a windows server.

Answer 1

I have the same issue, depending on what I put as a value in the "end" attribute of the print method, I got a threadLock:

from queue import LifoQueue
import threading
q = LifoQueue()

for i in range(100):
    q.put(i)

def process_job(q, threadName):
    while not q.empty():
        print(q.get(), end=' ')

workers = [
    threading.Thread(target=process_job, args=(q,'1')),
    threading.Thread(target=process_job, args=(q,'2')),
    threading.Thread(target=process_job, args=(q,'3')),
]

for w in workers:
    w.setDaemon(True)
    w.start()

The funniest part is that it works perfectly (as far as the end's value is blank " ").