What exactly is Python multiprocessing Module”s .join() Method Doing?

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Learning about Python Multiprocessing (from a PMOTW article) and would love some clarification on what exactly the join() method is doing.

In an old tutorial from 2008 it states that without the p.join() call in the code below, "the child process will sit idle and not terminate, becoming a zombie you must manually kill".

from multiprocessing import Process

def say_hello(name="world"):
    print "Hello, %s" % name

p = Process(target=say_hello)
p.start()
p.join()

I added a printout of the PID as well as a time.sleep to test and as far as I can tell, the process terminates on its own:

from multiprocessing import Process
import sys
import time

def say_hello(name="world"):
    print "Hello, %s" % name
    print "Starting:", p.name, p.pid
    sys.stdout.flush()
    print "Exiting :", p.name, p.pid
    sys.stdout.flush()
    time.sleep(20)

p = Process(target=say_hello)
p.start()
# no p.join()

within 20 seconds:

936 ttys000    0:00.05 /Library/Frameworks/Python.framework/Versions/2.7/Reso
938 ttys000    0:00.00 /Library/Frameworks/Python.framework/Versions/2.7/Reso
947 ttys001    0:00.13 -bash

after 20 seconds:

947 ttys001    0:00.13 -bash

Behavior is the same with p.join() added back at end of the file. Python Module of the Week offers a very readable explanation of the module; "To wait until a process has completed its work and exited, use the join() method.", but it seems like at least OS X was doing that anyway.

Am also wondering about the name of the method. Is the .join() method concatenating anything here? Is it concatenating a process with it"s end? Or does it just share a name with Python"s native .join() method?

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