Jupyter Notebook Multiprocessing code not working

Question

I am new in python i have Anaconda Pyton 3.9 I was studying about Multiprocessing.

When i try this code

from multiprocessing import Process # gerekli kütüphaneyi çağıracağız.

import time

def subfunc1():
    time.sleep(2)
    print("subfunc1: Baslatildi")
    time.sleep(2)
    print("subfunc1: Sonlandi")
    time.sleep(2)

def subfunc2():
    time.sleep(2)
    print("subfunc2: Baslatildi")
    time.sleep(2)
    print("subfunc2: Sonlandi")
    time.sleep(2)
    
def mainfunc():
    print("mainfunc: Baslatildi")
    pr1 = Process(target=subfunc1)
    pr2 = Process(target=subfunc2)
    pr1.start()
    pr2.start()
    print("mainfunc: Sonlandi")
    
if __name__ == '__main__': # Main kod bloğunun içerisindeyken main fonk çağır!
    mainfunc()

result is

    mainfunc: Baslatildi
    mainfunc: Sonlandi

When i use Visual Code with Python 3.9 i have a virtual and code works! Visual Code uses Anaconda's python 3.9 within a virtual env!

Could you please help me? Whey this code can't work properly in Jupyter Notebook?

Thanks

Answer 1

Am I correct in assuming you are running this on ms-windows or macOS?

In that case, multiprocessing will not work in an interactive interpreter like IPython. This is covered in the documentation, see the "note":

Functionality within this package requires that the __main__ module be importable by the children. This is covered in Programming guidelines however it is worth pointing out here. This means that some examples, such as the multiprocessing.pool.Pool examples will not work in the interactive interpreter.

This is caused by the spawn start method used on these operating systems.

One possible fix is to save you code in a script, and to make sure that creating multiprocessing objects is done within the __main__-block. Another is in the comment by Aaron below