在 python 中运行多线程已暂停

Question

我在python中测试多线程，但代码被挂起：

class MongoInsertThread(threading.Thread):
    def __init__(self,  queue, thread_id):
        super(MongoInsertThread, self).__init__()
        self.thread_id = thread_id
        self.queue = queue
    def run(self):
        print(self.thread_id,': ', self.queue.get())
def save_to_mongo_with_thread():
    q = queue.Queue()
    size = int(math.ceil(16 / 3))
    for e in range(size):
        for i in range(e * size, min((e + 1) * size, 16)):
            q.put([i], block=False)
        threads = []
        for i in range(size):
            threads.append(MongoInsertThread(q, i))
        for t in threads:
            t.start()
        for t in threads:
            t.join()
        print("+++++++++++++++++++++++")

结果是

我想要的，但程序没有结束，结果是：

0 :  [0]
1 :  [1]
2 :  [2]
3 :  [3]
4 :  [4]
5 :  [5]
+++++++++++++++++++++++
0 :  [6]
1 :  [7]
2 :  [8]
3 :  [9]
4 :  [10]
5 :  [11]
+++++++++++++++++++++++
0 :  [12]
1 :  [13]
2 :  [14]
3 :  [15]

但是它不打印最后+++++++++++++++++++++++，我该如何处理呢？

Answer 1

您正在调用q.put() 16次 - 每产生e in range(5) i in range(e * 5, (e + 1)*5)

1. i in range(0, 5)
2. i in range(5, 10)
3. i in range(10, 15)
4. i in range(15, 16)
5. i in range(20, 16)
6. i in range(25, 16)

这会将16值附加到q.但是，您创建25线程，其中包含对q.get()的关联25调用 - 但是一旦前16元素被get()块中删除。如果您使用q.get(block=False)代码将成功完成，但您将收到许多警告，从get()引发Empty。更改循环的循环条件

for i in range(size):
  threads.append(MongoInsertThread(q, i))

到range(e * size, min((e + 1) * size, 16))

将修复不匹配。但是，添加 break 语句以在添加和删除所有元素后停止最外层for循环也很有用16。

完整示例

class MongoInsertThread(threading.Thread):
    def __init__(self,  queue, thread_id):
        super(MongoInsertThread, self).__init__()
        self.thread_id = thread_id
        self.queue = queue
    def run(self):
        print(self.thread_id,': ', self.queue.get(block=False))
def save_to_mongo_with_thread():
    q = Queue.Queue()
    size = int(math.ceil(16 / 3))
    for e in range(5):
        if (e*size > 16): 
            break
        for i in range(e * size, min((e + 1) * size, 16)):
            q.put([i], block=False)
        threads = []
        for i in range(e * size, min((e + 1) * size, 16)):
            threads.append(MongoInsertThread(q, i))
        for t in threads:
            t.start()
        for t in threads:
            t.join()
        print("+++++++++++++++++++++++")

输出-

0: [0]
1: [1]
2: [2]
3: [3]
4: [4]
+++++++++++++++++++++++
5: [5]
6: [6]
7: [7]
8: [8]
9: [9]
+++++++++++++++++++++++
10: [10]
11: [11]
12: [12]
13: [13]
14: [14]
+++++++++++++++++++++++
15: [15]
+++++++++++++++++++++++

另请注意，我正在使用get(block = False)来帮助阐明未来的问题，但对于此示例来说，这是不必要的。