Thread reports dead after KeyboardInterrupt in thread.join()

Question

The code:

from threading import Thread
from time import sleep


def f() -> None:
    while True:
        sleep(0.4)
        print("Thread is running.")

thread = Thread(target=f, daemon=True)
thread.start()

try:
    thread.join()
except KeyboardInterrupt:
    print("Caught KeyboardInterrupt")

sleep(0.8)
print(f"thread._is_stopped = {thread._is_stopped}")
print(f"thread.is_alive() = {thread.is_alive()}")
sleep(0.8)

thread._is_stopped is set to True and thread.is_alive() reports False even though the thread is still alive and printing out messages to the console. This is the output:

python3 test.py
Thread is running.
Thread is running.
Thread is running.
^CCaught KeyboardInterrupt
Thread is running.
Thread is running.
thread._is_stopped = True
thread.is_alive() = False
Thread is running.
Thread is running.

Why is .is_alive() and ._is_stopped reporting that the thread is dead when the thread is clearly alive? Also if I .join() the thread again, it immediately returns which is undesirable for me.

Replacing the thread.join() with sleep(100), fixes the problem with is_alive() reporting False. The problem is that I want to know immediately when the thread really exists.

System:

• Ubuntu 22.04.2
• python 3.10.6 (pre-installed with Ubuntu)
• running it from bash (IDLE has problems with even causing a KeyboardInterrupts when joining a thread)