Waiting for threads to finish using join. Pretty basic

Question

I have a pretty basic assignment, but am having an issue making my main thread wait for all the other threads I spawn to complete.

This code does not do much of anything, it is just meant as a threading exercise.

Here is my code:

import time
from threading import Thread

def printNumbers(lowEnd, highEnd):
    while(lowEnd <= highEnd):
        print(repr(lowEnd))
        lowEnd += 1


countTo = 100000

#Test using 1 thread.        
startSingleThread = time.clock()
printNumbers(0,countTo)
elapsedSingleThread = (time.clock() - startSingleThread)

#Test using 10 threads
numberOfThreads      = 10
countAmountPerThread = countTo/numberOfThreads

startTenThread = time.clock()
for i in range(numberOfThreads):
    threadLowEnd  = i*countAmountPerThread
    threadHighEnd = (i+1)*countAmountPerThread
    t = Thread(target=printNumbers, args=(threadLowEnd,threadHighEnd,))
    t.start()

#Join all existing threads to main thread.
for thread in threading.enumerate():
    if thread is not threading.currentThread():
        thread.join()

elapsedTenThread = (time.clock() - startTenThread)

print("Time for 1 thread: " + repr(elapsedSingleThread))
print("time for 10 threads: " + repr(elapsedTenThread))

Answer 1

You can’t see the stderr because you’re printing so much to stdout, but you have this error:

Traceback (most recent call last):
  File "test.py", line 29, in <module>
    for thread in threading.enumerate():
NameError: name 'threading' is not defined

If I add import threading to the top, I get this output:

Time for 1 thread: 1.0224820000000001
time for 10 threads: 1.421281

…which might be what you were expecting to see, since it happens after all of the numbers are printed.