On 07/05/2017 09:56 AM, pozz wrote:
> It seems it works, but I'm not sure it is the correct way to share the
> variable self.cnt. It is only written in the long thread and only read
> in the main thread.
> Could a single Python instruction be interrupted (in this case, self.cnt
> = i)? Should I use a locking mechanism when reading/writing?
>
> What about if the variable is more complex, for example a list or
> dictionary? Even in this case, is it safe to avoid locking on a shared
> variable if the operation on the variable is performed in a single
> Python instruction?
I think it would be clearer if you used a queue. Here's an example of
simplified version showing how the communication might work:
test.py
---------------------------
from threading import Thread
from queue import Queue
from time import sleep
def main():
q = Queue()
t = Thread(target=worker, args=(q,))
t.start()
while True:
status = q.get()
if status < 0:
break
print(status)
t.join()
def worker(q, limit=5):
for i in range(limit):
sleep(1) # Simulate some work
q.put(i)
q.put(-1) # Some sort of value to indicate being finished
main()
--------------------------------
$ python3 test.py
0
1
2
3
4
Not sure if this helps, but I personally find it clearer than the shared
class variable method you're using.
Cheers,
Thomas
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