有没有办法杀死线程?
是否可以在不设置/检查任何标志/信号量/等的情况下终止正在运行的线程?
是否可以在不设置/检查任何标志/信号量/等的情况下终止正在运行的线程?
在Python和任何语言中突然杀死线程通常是一种不好的模式。请考虑以下情况:
如果你能负担得起(如果你正在管理自己的线程),处理这个问题的好方法是有一个exit_request标志,每个线程定期检查一次,看看它是否是时候退出了。
例如:
import threading
class StoppableThread(threading.Thread):
"""Thread class with a stop() method. The thread itself has to check
regularly for the stopped() condition."""
def __init__(self, *args, **kwargs):
super(StoppableThread, self).__init__(*args, **kwargs)
self._stop_event = threading.Event()
def stop(self):
self._stop_event.set()
def stopped(self):
return self._stop_event.is_set()
在此代码中,应在希望线程退出时调用该线程,并使用 等待线程正确退出。线程应定期检查停止标志。stop()
join()
但是,在某些情况下,您确实需要杀死线程。例如,当您包装一个忙于长时间调用的外部库,并且想要中断它时。
以下代码允许(但有一些限制)在 Python 线程中引发异常:
def _async_raise(tid, exctype):
'''Raises an exception in the threads with id tid'''
if not inspect.isclass(exctype):
raise TypeError("Only types can be raised (not instances)")
res = ctypes.pythonapi.PyThreadState_SetAsyncExc(ctypes.c_long(tid),
ctypes.py_object(exctype))
if res == 0:
raise ValueError("invalid thread id")
elif res != 1:
# "if it returns a number greater than one, you're in trouble,
# and you should call it again with exc=NULL to revert the effect"
ctypes.pythonapi.PyThreadState_SetAsyncExc(ctypes.c_long(tid), None)
raise SystemError("PyThreadState_SetAsyncExc failed")
class ThreadWithExc(threading.Thread):
'''A thread class that supports raising an exception in the thread from
another thread.
'''
def _get_my_tid(self):
"""determines this (self's) thread id
CAREFUL: this function is executed in the context of the caller
thread, to get the identity of the thread represented by this
instance.
"""
if not self.isAlive():
raise threading.ThreadError("the thread is not active")
# do we have it cached?
if hasattr(self, "_thread_id"):
return self._thread_id
# no, look for it in the _active dict
for tid, tobj in threading._active.items():
if tobj is self:
self._thread_id = tid
return tid
# TODO: in python 2.6, there's a simpler way to do: self.ident
raise AssertionError("could not determine the thread's id")
def raiseExc(self, exctype):
"""Raises the given exception type in the context of this thread.
If the thread is busy in a system call (time.sleep(),
socket.accept(), ...), the exception is simply ignored.
If you are sure that your exception should terminate the thread,
one way to ensure that it works is:
t = ThreadWithExc( ... )
...
t.raiseExc( SomeException )
while t.isAlive():
time.sleep( 0.1 )
t.raiseExc( SomeException )
If the exception is to be caught by the thread, you need a way to
check that your thread has caught it.
CAREFUL: this function is executed in the context of the
caller thread, to raise an exception in the context of the
thread represented by this instance.
"""
_async_raise( self._get_my_tid(), exctype )
(基于Tomer Filiba的Killable Threads。关于 返回值的引用似乎来自旧版本的 Python。PyThreadState_SetAsyncExc
如文档中所述,这不是一个灵丹妙药,因为如果线程在Python解释器外部繁忙,它将不会捕获中断。
此代码的一个很好的使用模式是让线程捕获特定异常并执行清理。这样,您可以中断任务,并且仍然可以进行适当的清理。
在我想杀死一个线程,但不想使用标志/锁/信号量/事件/任何东西的情况下,我将线程提升到完整的进程。对于仅使用几个线程的代码,开销并不是那么糟糕。
例如,这可以方便地终止执行阻塞I / O的帮助程序“线程”
转换是微不足道的:在相关代码中,将 all 替换为 和 all 替换为,并将 所需的调用添加到想要杀死其子进程的父进程threading.Thread
multiprocessing.Process
queue.Queue
multiprocessing.Queue
p.terminate()
p
请参阅有关多处理的
Python 文档。
例:
import multiprocessing
proc = multiprocessing.Process(target=your_proc_function, args=())
proc.start()
# Terminate the process
proc.terminate() # sends a SIGTERM