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

虽然它相当古老,但对一些人来说这可能是一个方便的解决方案:

一个扩展线程模块功能的小模块—— 允许一个线程在另一个线程的上下文中引发异常 线程。通过触发SystemExit,你最终可以杀死python线程。

import threading
import ctypes     

def _async_raise(tid, excobj):
    res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, ctypes.py_object(excobj))
    if res == 0:
        raise ValueError("nonexistent 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(tid, 0)
        raise SystemError("PyThreadState_SetAsyncExc failed")

class Thread(threading.Thread):
    def raise_exc(self, excobj):
        assert self.isAlive(), "thread must be started"
        for tid, tobj in threading._active.items():
            if tobj is self:
                _async_raise(tid, excobj)
                return

        # the thread was alive when we entered the loop, but was not found 
        # in the dict, hence it must have been already terminated. should we raise
        # an exception here? silently ignore?

    def terminate(self):
        # must raise the SystemExit type, instead of a SystemExit() instance
        # due to a bug in PyThreadState_SetAsyncExc
        self.raise_exc(SystemExit)

因此,它允许“线程在另一个线程的上下文中引发异常”,通过这种方式,被终止的线程可以处理终止,而无需定期检查中止标志。

然而,根据其原始来源,这段代码有一些问题。

The exception will be raised only when executing python bytecode. If your thread calls a native/built-in blocking function, the exception will be raised only when execution returns to the python code. There is also an issue if the built-in function internally calls PyErr_Clear(), which would effectively cancel your pending exception. You can try to raise it again. Only exception types can be raised safely. Exception instances are likely to cause unexpected behavior, and are thus restricted. For example: t1.raise_exc(TypeError) and not t1.raise_exc(TypeError("blah")). IMHO it's a bug, and I reported it as one. For more info, http://mail.python.org/pipermail/python-dev/2006-August/068158.html I asked to expose this function in the built-in thread module, but since ctypes has become a standard library (as of 2.5), and this feature is not likely to be implementation-agnostic, it may be kept unexposed.

其他回答

这似乎与windows 7上的pywin32一起工作

my_thread = threading.Thread()
my_thread.start()
my_thread._Thread__stop()

假设,你想有多个线程的同一个函数,这是IMHO最简单的实现通过id停止一个:

import time
from threading import Thread

def doit(id=0):
    doit.stop=0
    print("start id:%d"%id)
    while 1:
        time.sleep(1)
        print(".")
        if doit.stop==id:
            doit.stop=0
            break
    print("end thread %d"%id)

t5=Thread(target=doit, args=(5,))
t6=Thread(target=doit, args=(6,))

t5.start() ; t6.start()
time.sleep(2)
doit.stop =5  #kill t5
time.sleep(2)
doit.stop =6  #kill t6

这里的好处是,你可以有多个相同或不同的函数,并通过functionname。stop来停止它们

如果你想只有一个线程的函数,那么你不需要记住id。如果做了,就停下来。停止> 0。

实现一个线程是绝对可能的。方法,如下例代码所示:

import sys
import threading
import time


class StopThread(StopIteration):
    pass

threading.SystemExit = SystemExit, StopThread


class Thread2(threading.Thread):

    def stop(self):
        self.__stop = True

    def _bootstrap(self):
        if threading._trace_hook is not None:
            raise ValueError('Cannot run thread with tracing!')
        self.__stop = False
        sys.settrace(self.__trace)
        super()._bootstrap()

    def __trace(self, frame, event, arg):
        if self.__stop:
            raise StopThread()
        return self.__trace


class Thread3(threading.Thread):

    def _bootstrap(self, stop_thread=False):
        def stop():
            nonlocal stop_thread
            stop_thread = True
        self.stop = stop

        def tracer(*_):
            if stop_thread:
                raise StopThread()
            return tracer
        sys.settrace(tracer)
        super()._bootstrap()

###############################################################################


def main():
    test1 = Thread2(target=printer)
    test1.start()
    time.sleep(1)
    test1.stop()
    test1.join()
    test2 = Thread2(target=speed_test)
    test2.start()
    time.sleep(1)
    test2.stop()
    test2.join()
    test3 = Thread3(target=speed_test)
    test3.start()
    time.sleep(1)
    test3.stop()
    test3.join()


def printer():
    while True:
        print(time.time() % 1)
        time.sleep(0.1)


def speed_test(count=0):
    try:
        while True:
            count += 1
    except StopThread:
        print('Count =', count)

if __name__ == '__main__':
    main()

Thread3类运行代码的速度似乎比Thread2类快大约33%。

正如@Kozyarchuk的回答中提到的,安装跟踪工作。由于这个答案不包含代码,下面是一个工作就绪的示例:

import sys, threading, time 

class TraceThread(threading.Thread): 
    def __init__(self, *args, **keywords): 
        threading.Thread.__init__(self, *args, **keywords) 
        self.killed = False
    def start(self): 
        self._run = self.run 
        self.run = self.settrace_and_run
        threading.Thread.start(self) 
    def settrace_and_run(self): 
        sys.settrace(self.globaltrace) 
        self._run()
    def globaltrace(self, frame, event, arg): 
        return self.localtrace if event == 'call' else None
    def localtrace(self, frame, event, arg): 
        if self.killed and event == 'line': 
            raise SystemExit() 
        return self.localtrace 

def f(): 
    while True: 
        print('1') 
        time.sleep(2)
        print('2') 
        time.sleep(2)
        print('3') 
        time.sleep(2)

t = TraceThread(target=f) 
t.start() 
time.sleep(2.5) 
t.killed = True

它在输出1和2之后停止。3不打印。

from ctypes import *
pthread = cdll.LoadLibrary("libpthread-2.15.so")
pthread.pthread_cancel(c_ulong(t.ident))

t是线程对象。

阅读python源代码(Modules/threadmodule.c和python /thread_pthread.h),你可以看到Thread。Ident是一个pthread_t类型,所以你可以使用libpthread在python中做任何pthread可以做的事情。