我对Python和多线程编程非常陌生。基本上,我有一个脚本,将文件复制到另一个位置。我想把这个放在另一个线程,这样我就可以输出....表示脚本仍在运行。

我遇到的问题是,如果文件不能复制,它将抛出异常。如果在主线程中运行,这是可以的;但是,使用以下代码是无效的:

try:
    threadClass = TheThread(param1, param2, etc.)
    threadClass.start()   ##### **Exception takes place here**
except:
    print "Caught an exception"

在线程类本身中,我试图重新抛出异常,但它不起作用。我在这里看到有人问类似的问题,但他们似乎都在做一些比我试图做的更具体的事情(我不太理解所提供的解决方案)。我看到有人提到sys.exc_info()的用法,但我不知道在哪里或如何使用它。

编辑:线程类的代码如下:

class TheThread(threading.Thread):
    def __init__(self, sourceFolder, destFolder):
        threading.Thread.__init__(self)
        self.sourceFolder = sourceFolder
        self.destFolder = destFolder
    
    def run(self):
        try:
           shul.copytree(self.sourceFolder, self.destFolder)
        except:
           raise

当前回答

这个问题有很多非常奇怪复杂的答案。我是不是把它简化了,因为对我来说,这似乎对大多数事情都足够了。

from threading import Thread

class PropagatingThread(Thread):
    def run(self):
        self.exc = None
        try:
            if hasattr(self, '_Thread__target'):
                # Thread uses name mangling prior to Python 3.
                self.ret = self._Thread__target(*self._Thread__args, **self._Thread__kwargs)
            else:
                self.ret = self._target(*self._args, **self._kwargs)
        except BaseException as e:
            self.exc = e

    def join(self, timeout=None):
        super(PropagatingThread, self).join(timeout)
        if self.exc:
            raise self.exc
        return self.ret

如果你确定你只会在一个或另一个版本的Python上运行,你可以将run()方法减少到只有被破坏的版本(如果你只在3之前的Python版本上运行),或者仅仅是干净的版本(如果你只在3开始的Python版本上运行)。

使用示例:

def f(*args, **kwargs):
    print(args)
    print(kwargs)
    raise Exception('I suck at this')

t = PropagatingThread(target=f, args=(5,), kwargs={'hello':'world'})
t.start()
t.join()

当您加入时,您将看到在另一个线程上引发异常。

如果您正在使用six或仅在Python 3上使用,则可以改进重新引发异常时获得的堆栈跟踪信息。您可以将内部异常包装在一个新的外部异常中,而不是仅在连接点处使用堆栈,并使用

six.raise_from(RuntimeError('Exception in thread'),self.exc)

or

raise RuntimeError('Exception in thread') from self.exc

其他回答

我使用这个版本,它是最小的,它工作得很好。

class SafeThread(threading.Thread):
    def __init__(self, *args, **kwargs):
        super(SafeThread, self).__init__(*args, **kwargs)
        self.exception = None

    def run(self) -> None:
        try:
            super(SafeThread, self).run()
        except Exception as ex:
            self.exception = ex
            traceback.print_exc()

    def join(self, *args, **kwargs) -> None:
        super(SafeThread, self).join(*args, **kwargs)
        if self.exception:
            raise self.exception

要使用它,只需替换线程。带安全线程的线程

t = SafeThread(target = some_function, args = (some, args,))
t.start()
# do something else here if you want as the thread runs in the background
t.join()

类似于RickardSjogren的方法,没有Queue, sys等,但也没有一些信号监听器:直接执行一个异常处理程序,对应于一个异常块。

#!/usr/bin/env python3

import threading

class ExceptionThread(threading.Thread):

    def __init__(self, callback=None, *args, **kwargs):
        """
        Redirect exceptions of thread to an exception handler.

        :param callback: function to handle occured exception
        :type callback: function(thread, exception)
        :param args: arguments for threading.Thread()
        :type args: tuple
        :param kwargs: keyword arguments for threading.Thread()
        :type kwargs: dict
        """
        self._callback = callback
        super().__init__(*args, **kwargs)

    def run(self):
        try:
            if self._target:
                self._target(*self._args, **self._kwargs)
        except BaseException as e:
            if self._callback is None:
                raise e
            else:
                self._callback(self, e)
        finally:
            # Avoid a refcycle if the thread is running a function with
            # an argument that has a member that points to the thread.
            del self._target, self._args, self._kwargs, self._callback

只有自我。_callback和run()中的except块是普通threading.Thread之外的。

使用异常存储包装线程。

import threading
import sys
class ExcThread(threading.Thread):

    def __init__(self, target, args = None):
        self.args = args if args else []
        self.target = target
        self.exc = None
        threading.Thread.__init__(self)

    def run(self):
        try:
            self.target(*self.args)
            raise Exception('An error occured here.')
        except Exception:
            self.exc=sys.exc_info()

def main():
    def hello(name):
        print(!"Hello, {name}!")
    thread_obj = ExcThread(target=hello, args=("Jack"))
    thread_obj.start()

    thread_obj.join()
    exc = thread_obj.exc
    if exc:
        exc_type, exc_obj, exc_trace = exc
        print(exc_type, ':',exc_obj, ":", exc_trace)

main()

我喜欢这门课:

https://gist.github.com/earonesty/b88d60cb256b71443e42c4f1d949163e

import threading
from typing import Any


class PropagatingThread(threading.Thread):
    """A Threading Class that raises errors it caught, and returns the return value of the target on join."""

    def __init__(self, *args, **kwargs):
        self._target = None
        self._args = ()
        self._kwargs = {}
        super().__init__(*args, **kwargs)
        self.exception = None
        self.return_value = None
        assert self._target

    def run(self):
        """Don't override this if you want the behavior of this class, use target instead."""
        try:
            if self._target:
                self.return_value = self._target(*self._args, **self._kwargs)
        except Exception as e:
            self.exception = e
        finally:
            # see super().run() for why this is necessary
            del self._target, self._args, self._kwargs

    def join(self, timeout=None) -> Any:
        super().join(timeout)
        if self.exception:
            raise self.exception
        return self.return_value

在Python 3.8中,我们可以使用线程。Excepthook在所有子线程中钩住未捕获的异常!例如,

threading.excepthook = thread_exception_handler

推荐人:https://stackoverflow.com/a/60002752/5093308