threading.excepthook args.exc_traceback 为 None

问：

我正在尝试覆盖.它有点工作，但我的接收作为回溯。Python 文档说这是可能的。但是，为什么呢？我怎样才能得到真正的回溯？threading.excepthookcustom_hook()Nonecustom_hook()

我的最终目标是为每个堆栈轨道打印一个时间戳（对于系统异常和我的自定义异常）。输出需要转到 。stderr

如果我运行以下代码：

from time import sleep
import threading
import traceback


# target function that raises an exception
def work():
    print('Working...')
    sleep(1)
    # rise an exception
    raise Exception('Something bad happened')


# custom exception hook
def custom_hook(args):
    # report the failure
    print('timestamp')
    print(traceback.print_tb(args.exc_traceback))


def main():
    # set the exception hook
    threading.excepthook = custom_hook
    # create a thread
    thread = threading.Thread(target=work)
    # run the thread
    thread.start()
    # wait for the thread to finish
    thread.join()
    # continue on
    print('Continuing on...')


if __name__ == "__main__":
    main()

我得到这个输出：

/Users/msarrel/PycharmProjects/pychansim/venv/bin/python /Users/msarrel/Library/Application Support/JetBrains/PyCharm2023.2/scratches/scratch_1.py 
Working...
timestamp
None
Continuing on...
  File "/usr/local/Cellar/[email protected]/3.9.18/Frameworks/Python.framework/Versions/3.9/lib/python3.9/threading.py", line 980, in _bootstrap_inner
    self.run()
  File "/usr/local/Cellar/[email protected]/3.9.18/Frameworks/Python.framework/Versions/3.9/lib/python3.9/threading.py", line 917, in run
    self._target(*self._args, **self._kwargs)
  File "/Users/msarrel/Library/Application Support/JetBrains/PyCharm2023.2/scratches/scratch_1.py", line 11, in work
    raise Exception('Something bad happened')

Process finished with exit code 0

出于某种原因，回溯打印在 .thread.join()

如果我不尝试在以下位置打印回溯：custom_hook()

from time import sleep
import threading
# import traceback


# target function that raises an exception
def work():
    print('Working...')
    sleep(1)
    # rise an exception
    raise Exception('Something bad happened')


# custom exception hook
def custom_hook(args):
    # report the failure
    print('timestamp')
    # print(traceback.print_tb(args.exc_traceback))


def main():
    # set the exception hook
    threading.excepthook = custom_hook
    # create a thread
    thread = threading.Thread(target=work)
    # run the thread
    thread.start()
    # wait for the thread to finish
    thread.join()
    # continue on
    print('Continuing on...')


if __name__ == "__main__":
    main()

我得到以下输出：

/Users/msarrel/PycharmProjects/pychansim/venv/bin/python /Users/msarrel/Library/Application Support/JetBrains/PyCharm2023.2/scratches/scratch_1.py 
Working...
timestamp
Continuing on...

Process finished with exit code 0

在这种情况下，根本不会打印回溯...

为什么？