是否有可能终止一个正在运行的线程而不设置/检查任何标志/信号/等等?
当前回答
这里还有另一种方法,但代码非常干净和简单,适用于2021年的Python 3.7:
import ctypes
def kill_thread(thread):
"""
thread: a threading.Thread object
"""
thread_id = thread.ident
res = ctypes.pythonapi.PyThreadState_SetAsyncExc(thread_id, ctypes.py_object(SystemExit))
if res > 1:
ctypes.pythonapi.PyThreadState_SetAsyncExc(thread_id, 0)
print('Exception raise failure')
改编自:https://www.geeksforgeeks.org/python-different-ways-to-kill-a-thread/
其他回答
最简单的方法是:
from threading import Thread
from time import sleep
def do_something():
global thread_work
while thread_work:
print('doing something')
sleep(5)
print('Thread stopped')
thread_work = True
Thread(target=do_something).start()
sleep(5)
thread_work = False
Python版本:3.8
使用守护线程来执行我们想要的,如果我们想要终止守护线程,我们只需要让父线程退出,然后系统就会终止父线程创建的守护线程。
还支持协程和协程函数。
def main():
start_time = time.perf_counter()
t1 = ExitThread(time.sleep, (10,), debug=False)
t1.start()
time.sleep(0.5)
t1.exit()
try:
print(t1.result_future.result())
except concurrent.futures.CancelledError:
pass
end_time = time.perf_counter()
print(f"time cost {end_time - start_time:0.2f}")
下面是ExitThread源代码
import concurrent.futures
import threading
import typing
import asyncio
class _WorkItem(object):
""" concurrent\futures\thread.py
"""
def __init__(self, future, fn, args, kwargs, *, debug=None):
self._debug = debug
self.future = future
self.fn = fn
self.args = args
self.kwargs = kwargs
def run(self):
if self._debug:
print("ExitThread._WorkItem run")
if not self.future.set_running_or_notify_cancel():
return
try:
coroutine = None
if asyncio.iscoroutinefunction(self.fn):
coroutine = self.fn(*self.args, **self.kwargs)
elif asyncio.iscoroutine(self.fn):
coroutine = self.fn
if coroutine is None:
result = self.fn(*self.args, **self.kwargs)
else:
result = asyncio.run(coroutine)
if self._debug:
print("_WorkItem done")
except BaseException as exc:
self.future.set_exception(exc)
# Break a reference cycle with the exception 'exc'
self = None
else:
self.future.set_result(result)
class ExitThread:
""" Like a stoppable thread
Using coroutine for target then exit before running may cause RuntimeWarning.
"""
def __init__(self, target: typing.Union[typing.Coroutine, typing.Callable] = None
, args=(), kwargs={}, *, daemon=None, debug=None):
#
self._debug = debug
self._parent_thread = threading.Thread(target=self._parent_thread_run, name="ExitThread_parent_thread"
, daemon=daemon)
self._child_daemon_thread = None
self.result_future = concurrent.futures.Future()
self._workItem = _WorkItem(self.result_future, target, args, kwargs, debug=debug)
self._parent_thread_exit_lock = threading.Lock()
self._parent_thread_exit_lock.acquire()
self._parent_thread_exit_lock_released = False # When done it will be True
self._started = False
self._exited = False
self.result_future.add_done_callback(self._release_parent_thread_exit_lock)
def _parent_thread_run(self):
self._child_daemon_thread = threading.Thread(target=self._child_daemon_thread_run
, name="ExitThread_child_daemon_thread"
, daemon=True)
self._child_daemon_thread.start()
# Block manager thread
self._parent_thread_exit_lock.acquire()
self._parent_thread_exit_lock.release()
if self._debug:
print("ExitThread._parent_thread_run exit")
def _release_parent_thread_exit_lock(self, _future):
if self._debug:
print(f"ExitThread._release_parent_thread_exit_lock {self._parent_thread_exit_lock_released} {_future}")
if not self._parent_thread_exit_lock_released:
self._parent_thread_exit_lock_released = True
self._parent_thread_exit_lock.release()
def _child_daemon_thread_run(self):
self._workItem.run()
def start(self):
if self._debug:
print(f"ExitThread.start {self._started}")
if not self._started:
self._started = True
self._parent_thread.start()
def exit(self):
if self._debug:
print(f"ExitThread.exit exited: {self._exited} lock_released: {self._parent_thread_exit_lock_released}")
if self._parent_thread_exit_lock_released:
return
if not self._exited:
self._exited = True
if not self.result_future.cancel():
if self.result_future.running():
self.result_future.set_exception(concurrent.futures.CancelledError())
正如其他人所提到的,规范是设置一个停止标志。对于一些轻量级的东西(没有Thread的子类化,没有全局变量),lambda回调是一个选项。(注意if stop()中的括号。)
import threading
import time
def do_work(id, stop):
print("I am thread", id)
while True:
print("I am thread {} doing something".format(id))
if stop():
print(" Exiting loop.")
break
print("Thread {}, signing off".format(id))
def main():
stop_threads = False
workers = []
for id in range(0,3):
tmp = threading.Thread(target=do_work, args=(id, lambda: stop_threads))
workers.append(tmp)
tmp.start()
time.sleep(3)
print('main: done sleeping; time to stop the threads.')
stop_threads = True
for worker in workers:
worker.join()
print('Finis.')
if __name__ == '__main__':
main()
将print()替换为始终刷新的pr()函数(sys.stdout.flush())可以提高shell输出的精度。
(仅在Windows/Eclipse/Python3.3上测试)
你不应该在没有与线程合作的情况下强行终止线程。
杀死一个线程消除了try/finally阻塞设置的任何保证,所以你可能会让锁锁定,文件打开等等。
唯一可以认为强制终止线程是一个好主意的情况是快速终止程序,但绝不是单个线程。
下面的方法可以用来杀死一个线程:
kill_threads = False
def doSomething():
global kill_threads
while True:
if kill_threads:
thread.exit()
......
......
thread.start_new_thread(doSomething, ())
这甚至可以用于从主线程终止代码写在另一个模块中的线程。我们可以在该模块中声明一个全局变量,并使用它来终止在该模块中生成的线程。
我通常使用它在程序出口终止所有线程。这可能不是终止线程的完美方法,但可能有帮助。
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