在新生成的进程中生成线程并使用 print 在 Python 中查看线程状态

Question

我有一个创建 2 个新进程的 python 脚本。然后，在每个新进程中，我创建 3 个线程。

import os
import threading
import multiprocessing as mp
import time


def extra_threads():
    x = 7
    while x != 0:
        x -= 1
        for specific_thread in threading.enumerate():
            print('THREAD:', specific_thread, f'X Value: {x},', os.getpid())


def new_process():
    print('PROCESS: New Process PID:', os.getpid())
    print('PROCESS: Thread Count:',
          threading.active_count())
    for specific_thread in threading.enumerate(): 
        print('PROCESS:', specific_thread)
    print('PROCESS: CREATING 3 ADDITIONAL THREADS IN PID:', os.getpid())

    for y in range(3):
        t = threading.Thread(target=extra_threads)
        t.setDaemon(True)
        t.start()

    print('PROCESS: Thread Count: ', threading.active_count(), 'PID:', os.getpid())

    while True:
        pass


if __name__ == '__main__':
    # display information about this process
    print('Parent Process ID: ', os.getpid())  # Get's the unique Process ID of this process
    print('Parent Thread Count: ', threading.active_count())  # Shows that it is initially 1 thread to his process

    for thread in threading.enumerate():
        print('MAIN PROGRAM THREADS:', thread)  # Prints information about each of those threads

    print('\nSTARTING 2 NEW PROCESSES...')
    print()
    for z in range(2):
        print(f'Starting {z + 1} New Process...')
        print()
        mp.Process(target=new_process).start()
        time.sleep(1)
        print()

当我查看终端的进程时，输出符合预期。 我有 2 个进程 (ps -eF) 和每个进程的 3 个线程（当我运行 ps -L 时）。

但是，对于每个进程中的每个线程，打印语句（在 extra_thread() 函数中）在终端出现两次。这可以通过重复多次打印的 X 值来观察。

有人能解释为什么会这样吗？

THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 6, 449
**THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 6, 449**
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 6, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 5, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 6, 449
**THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 6, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 6, 449**
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 6, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 5, 449
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 6, 449
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 5, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 5, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 5, 449
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 5, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 4, 449
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 5, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 4, 449
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 5, 449
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 4, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 4, 449
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 4, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 4, 449
THREAD: <_MainThread(MainThread, started 140020333217600)> X Value: 3, 449
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 3, 449
...

THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 5, 450
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 5, 450
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 5, 450
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 4, 450
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 5, 450
THREAD: <Thread(Thread-2, started daemon 140020317751040)> X Value: 4, 450
THREAD: <Thread(Thread-3, started daemon 140020309296896)> X Value: 4, 450
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 4, 450
THREAD: <Thread(Thread-1, started daemon 140020326205184)> X Value: 3, 450

是不是因为在新进程线程中调用了print语句（打印“there”也打印在父进程中？

另外，线程信息中“started daemon”后面的数字是多少？如果是内存地址，为什么跨不同进程的子线程都一样？ （主线程地址与生成的所有 2 个进程不同，这是意料之中的）。

谢谢！

Answer 1

您的日志与我预期的一样。请记住，每个线程都将打印每个循环中所有线程的完整清单。因此，我希望每个进程看到 28 个日志条目（4 个线程 x 7 次迭代）。

数字是进程本地的“线程标识符”。如果您在 LInux 上，这三个进程都是彼此的精确副本，因此执行相同的代码将始终以相同的地址结束。