python3.x multiprocessing cycling without “if __name__ == '__main__':”

Question

I have this file (it doesn\'t make any useful work, it\'s only for learning):

import multiprocessing,sys
def parent(numproc=2):
    print (\'at start\')
             


        

Answer 1

The subprocess has the following __name__: __parents_main__ and not __main__ any more. This is why your process does not loop when you are testign the __name__ variable.

For more information on this have a look to the chapter Safe importing of main module

Answer 2

This is an issue with multiprocessing on MS Windows: the main module is imported by the child tasks, so any code not protected by the if __name__ . . . clause gets run again, resulting in an infinite loop.