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
多处理。进程可以p.terminate()
如果我想杀死一个线程,但不想使用标志/锁/信号/信号量/事件/任何东西,我就把线程提升到完整的进程。对于只使用几个线程的代码,开销并没有那么糟糕。
例如,这可以方便地终止执行阻塞I/O的助手“线程”
转换很简单:在相关代码中替换所有线程。多线程线程。进程和所有队列。多处理队列。排队并将p.t terminate()所需的调用添加到想要杀死子进程p的父进程中
关于多处理,请参阅Python文档。
例子:
import multiprocessing
proc = multiprocessing.Process(target=your_proc_function, args=())
proc.start()
# Terminate the process
proc.terminate() # sends a SIGTERM
如果您确实需要终止子任务的能力,请使用另一种实现。Multiprocessing和gevent都支持不加选择地杀死一个“线程”。
Python的线程不支持取消。不要尝试。你的代码很可能死锁、损坏或泄漏内存,或者有其他意想不到的“有趣的”难以调试的效果,这种情况很少发生,而且不确定。
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。
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)
这是基于thread2—可杀死线程ActiveState配方。
您需要调用PyThreadState_SetAsyncExc(),它只能通过ctypes模块使用。
这只在Python 2.7.3上进行了测试,但它很可能与最近的其他2一起工作。x版本。PyThreadState_SetAsyncExc()仍然存在于Python 3中以实现向后兼容性(但我还没有测试它)。
import ctypes
def terminate_thread(thread):
"""Terminates a python thread from another thread.
:param thread: a threading.Thread instance
"""
if not thread.isAlive():
return
exc = ctypes.py_object(SystemExit)
res = ctypes.pythonapi.PyThreadState_SetAsyncExc(
ctypes.c_long(thread.ident), exc)
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(thread.ident, None)
raise SystemError("PyThreadState_SetAsyncExc failed")
推荐文章
- 证书验证失败:无法获得本地颁发者证书
- 当使用pip3安装包时,“Python中的ssl模块不可用”
- 无法切换Python与pyenv
- Python if not == vs if !=
- 如何从scikit-learn决策树中提取决策规则?
- 为什么在Mac OS X v10.9 (Mavericks)的终端中apt-get功能不起作用?
- 将旋转的xtick标签与各自的xtick对齐
- 为什么元组可以包含可变项?
- 如何合并字典的字典?
- 如何创建类属性?
- 不区分大小写的“in”
- 在Python中获取迭代器中的元素个数
- 自动化invokerrequired代码模式
- 解析日期字符串并更改格式
- 使用try和。Python中的if