[Python] Why doesn't multiprocessing.Process.start() in Python guarantee that the process has...

Here is a code to demo my question:

from multiprocessing import Process


def worker():
print("Worker running")


if __name__ == "__main__":
p = Process(target=worker)
p.start()
input("1...")
input("2...")
p.join()


Note, ran on Python 3.13, Windows x64.

And the output I got is (after inputting Enter twice):

1...
2...
Worker running

Process finished with exit code 0


From the output, we can see the process actually initialized and started to run after the 2nd input. While I thought start() should block and guarantee the child process is fully initialized.

Is this a normal behavior of Python multiprocessing?

Because if Threading is used here instead, this issue seldom occur. I always get the thread run before the line input("1...").

May I ask, if Process.start() doesn't guarantee the process is fully-started, how should we code to ensure the child process is actually running before proceeding in the parent?

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