Runs a parallelizable function in batches of threads, waiting for each batch to finish. This allows the full resources of the computer to be used, without overwheming it when you have hundreds or thousands of threads to run.

RunBatchesOfThreads.py

import threading
import os

# Normally this would be some busier function...  Here it is a stub.
def PlotAlphaMELTS(PathName):
    print PathName

# How many threads we want.
NumThreads = 10
# Counter for the thread in the loop.
ThreadCount = 0
# List of the threads.
threads = [None]*NumThreads

# You need a different parameter to each thread to make it do something different.
params = range(100)

# This part is really processor intensive, so let's multithread it.
for p in params:
    # Set up a thread.
    threads[ThreadCount] = threading.Thread(target=PlotAlphaMELTS, args=(p,))
    ThreadCount += 1
    
    # After making NumThreads threads, then we start them all.
    if ThreadCount % NumThreads == 0:
       for t in threads:
           # daemon mode so they run simultaneously.
           t.daemon = True
           t.start()
       # Now they are running.  Wait until they all finish.
       for t in threads:
           t.join()
       # And reset the counter so we do a new batch
       ThreadCount = 0