【 在 giantman 的大作中提到: 】
: 开始学习python中的多线程，可是我发现按照书上的例子，将子线程的daemon无论设成True还是False，结果都一样，子线程都不能随主线程的结束而结束，而且每次运行，结果都不完全一样，不知道是怎么回事？
: 程序如下：
: import threading
: ...................

我用 Python 3.7.3 在 Mac 平台下的 PyCharm IDE 中测试，结果完全符合预期. 可能你的Python环境有问题。
代码：
```
import sys
import threading
import time

print(f'\nPython version: {sys.version}\n', end='', flush=True)


def reading(msg: str):
    count = 3
    for i in range(count):
        print(f'{msg}: reading {i+1}/{count}\n', end='', flush=True)
        time.sleep(1)


def test(thread_count: int, is_daemon: bool) -> None:
    print(f'\n-------- setDaemon({is_daemon}) --------\n', end='', flush=True)
    for index in range(thread_count):
        r = threading.Thread(target=reading, args=[f'Thread {index+1}'])
        r.setDaemon(is_daemon)
        r.start()
    print('Main thread: The End\n', end='', flush=True)


test(5, True)

```

运行结果：
```
/Users/abc/project/pythonProject/test/venv/bin/python /Users/abc/project/pythonProject/test/my_daemon.py

Python version: 3.7.3 (default, Apr 24 2020, 18:51:23)
[Clang 11.0.3 (clang-1103.0.32.62)]

-------- setDaemon(True) --------
Thread 1: reading 1/3
Thread 2: reading 1/3
Thread 3: reading 1/3
Thread 4: reading 1/3
Thread 5: reading 1/3
Main thread: The End

Process finished with exit code 0
```

代码最后一行改为 `test(5, False)` 后，运行结果:
```
/Users/abc/project/pythonProject/test/venv/bin/python /Users/abc/project/pythonProject/test/my_daemon.py

Python version: 3.7.3 (default, Apr 24 2020, 18:51:23)
[Clang 11.0.3 (clang-1103.0.32.62)]

-------- setDaemon(False) --------
Thread 1: reading 1/3
Thread 2: reading 1/3
Thread 3: reading 1/3
Thread 4: reading 1/3
Thread 5: reading 1/3
Main thread: The End
Thread 1: reading 2/3
Thread 2: reading 2/3
Thread 5: reading 2/3
Thread 4: reading 2/3
Thread 3: reading 2/3
Thread 2: reading 3/3
Thread 5: reading 3/3
Thread 1: reading 3/3
Thread 3: reading 3/3
Thread 4: reading 3/3

Process finished with exit code 0

```
--
修改:galaxy123 FROM 74.88.40.*
FROM 74.88.40.*