title: Python 3.5 Threading: Is this implemented correctly?
body: <p>I am trying to investigate threading by looking for primes in lists of random values.  I expected to find that using threading made this faster but the times for threaded and un-threaded are the same. Is this because I have implemented this incorrectly?  How can I demonstrate the benefits of threading using an example like this?</p>
  
  <pre><code>import time
  import threading
  from math import sqrt
  from random import randint
  
  def findPrimes(aList):
      for testValue in aList:
          isPrime = True
          for i in range(2,int(sqrt(testValue)+1)):
              if testValue % i == 0:
                  isPrime = False
          if isPrime:
              #print(testValue)
              pass
  
  testValues1 = []
  testValues2 = []
  for i in range(1000):
      testValues1.append(randint(10,100))
      testValues2.append(randint(10,100))
  
  
  t = time.process_time()
  findPrimes(testValues1)
  findPrimes(testValues2)
  print('The long way',time.process_time() - t) # runs in 0.006 to 0.007
  
  
  t = time.process_time()
  thread1 = threading.Thread(target=findPrimes(testValues1))
  thread2 = threading.Thread(target=findPrimes(testValues2))
  thread1.start()
  thread2.start()
  print('The threading way',time.process_time() - t) # also runs in 0.006 to 0.007
  </code></pre>