[Python] Python threading. How do I lock a thread?

I'm trying to understand the basics of threading and concurrency. I want a simple case where two threads repeatedly try to access one shared resource.

The code:

import threading

class Thread(threading.Thread):
def __init__(self, t, *args):
threading.Thread.__init__(self, target=t, args=args)
self.start()
count = 0
lock = threading.Lock()

def increment():
global count
lock.acquire()
try:
count += 1
finally:
lock.release()

def bye():
while True:
increment()

def hello_there():
while True:
increment()

def main():
hello = Thread(hello_there)
goodbye = Thread(bye)

while True:
print count

if __name__ == '__main__':
main()


So, I have two threads, both trying to increment the counter. I thought that if thread 'A' called increment(), the lock would be established, preventing 'B' from accessing until 'A' has released.

Running the makes it clear that this is not the case. You get all of the random data race-ish increments.

How exactly is the lock object used?

Additionally, I've tried putting the locks inside of the thread functions, but still no luck.

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