为什么这个队列会这样？

Question

我正在编写一个从多处理队列中提取的对象，我发现当我运行这段代码时，我得到了data = []。然而，如果我告诉程序在指定的地方睡一会儿，我会得到data = [1,2]，这是应该的。你知道吗

from multiprocessing import Queue
import time

q = Queue()
taken = 0
data = []

for i in [1,2]:
  q.put(i)
# time.sleep(1) making this call causes the correct output 
while not q.empty() and taken < 2:
   try:
     data.append(q.get(timeout=1))
     taken+=1
   except Empty:
     continue

**EDIT:**while循环之前有print语句时也会发生这种情况。这表明对q.put（）的调用发生了一些问题，但我找不到任何关于这个问题的文档。你知道吗

Answer 1

在docs中提到了多处理队列你知道吗

Note When an object is put on a queue, the object is pickled and a background thread later flushes the pickled data to an underlying pipe. This has some consequences which are a little surprising, but should not cause any practical difficulties – if they really bother you then you can instead use a queue created with a manager.

1. After putting an object on an empty queue there may be an infinitesimal delay before the queue’s empty() method returns False and get_nowait() can return without raising Queue.Empty. ...