While learning Python's threading module I've run a simple test. Interesting that the threads are running sequentially and not parallel. Is it possible to modify this test code so a program executes the threads in same fashion as multiprocessing does: in parallel?

import threadingdef mySlowFunc(arg):print "\nStarting...", argm=0for i in range(arg):m+=iprint '\n...Finishing', argmyList =[35000000, 45000000, 55000000]for each in myList:thread = threading.Thread(target=mySlowFunc, args=(each,) )thread.daemon = Truethread.start()thread.join()print "\n Happy End \n"

REVISED CODE:

This version of the code will initiate 6 'threads' running in 'parallel'. But even while there will be 6 threads only two CPU's threads are actually used (6 other Physical CPU threads will be idling and doing nothing).

import threadingdef mySlowFunc(arg):print "\nStarting " + str(arg) + "..."m=0for i in range(arg):m+=iprint '\n...Finishing ' + str(arg)myList =[35000000, 45000000, 55000000, 25000000, 75000000, 65000000]for each in myList:thread = threading.Thread(target=mySlowFunc, args=(each,) )thread.daemon = Falsethread.start()print "\n Bottom of script reached \n"

From the docs for the join method:

Wait until the thread terminates. This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception – or until the optional timeout occurs.

Just create a list of threads and join them after launching every single one of them.

Edit:

The threads are executing in parallel, you can think of python's threads like a computer with a single core, the thing is, python's threads are best for IO operations (reading/writing a big file, sending data through a socket, that sort of thing). If you want CPU power you need to use the multiprocessing module