The idle queue isn't 100% a queue

 

    This week, I ran into a strange problem with a multi-threading Python case from a partner.

def foo():
for i in range(10):
    print i

# call from main thread
foo()

# call from separate thread
import threading
mythread = threading.Thread(target=foo)
mythread.start()

 

The output is quite strange:

0
1
2
3
4
5
6
7
8
9

9
8
7
6
5
4
3
2
1
0

    The child thread's output order is reversed, how did that happen?

    After spending some time with our engineers, we found that Maya will treat the higher priority queue as a stack for better performance. The Python I/O output is considered as a high priority event and it is in the high priority idle queue.

    If you are using multi-threading in your code or idle queue, you may want to take this into consideration.