python - 如何从线程队列Python内部停止线程

Question

我遇到的情况是，当线程与当前正在运行/正在执行的线程内的条件匹配时，我需要停止执行线程:

这是我的意思的例子:

• 我们有 5 个数字的列表，从 1 到 5。
• 我们将它们排队并与 Run_Calc 函数中的 10 个线程数一起处理它们。
• 在 Run_Calc 中，我希望我的线程在匹配 3 条件时停止

import threading,queue

q = queue.Queue()
numbers = [1,2,3,4,5]

for each_num in numbers:
    q.put(each_num)

def Run_Calc(no):
    print("NO IS : {}".format(no))
    if no == 3:
        print("YES I WANT TO EXIT HERE and DONT WANT TO EXECUTE 4,5")

def ProcessThreading():
    while not q.empty():
        get_number = q.get()
        Run_Calc(get_number)

th_list = []
for i in range(10):
    t = threading.Thread(target=ProcessThreading)
    th_list.append(t)
    t.start()
for th in th_list:
    th.join()

• 输出:

NO IS : 1
NO IS : 2
NO IS : 3
YES I WANT TO EXIT HERE and DONT WANT TO EXECUTE 4,5
NO IS : 4
NO IS : 5

• 如何实现它？

Answer 1

在某些情况下，即使线程是按顺序实例化的，线程也可能会以“谁跑得更快”的方式进行竞争。
对于您的简单情况，请使用 threading.Event对象在特定事件上同步线程:

import queue
from threading import Thread, Event

q = queue.Queue()
numbers = [1, 2, 3, 4, 5]

for each_num in numbers:
    q.put(each_num)


def run_calc(num, e):
    print("NO IS : {}".format(num))
    if num == 3:
        e.set()
        print("YES I WANT TO EXIT HERE and DONT WANT TO EXECUTE 4,5")


def process_thread(e):
    while not q.empty():
        if e.is_set():
            break
        num = q.get()
        run_calc(num, e)


th_list = []

e = Event()
for i in range(10):
    t = Thread(target=process_thread, args=(e,))
    th_list.append(t)
    t.start()

for th in th_list:
    th.join()

示例输出:

NO IS : 1
NO IS : 2
NO IS : 3
YES I WANT TO EXIT HERE and DONT WANT TO EXECUTE 4,5