title: Fail to use global variable to count thread
body: <p>I was trying to use a global variable to count the number of thread.</p>
  
  <pre><code>l = range(1, 11)
  clientCount = 0
  listLock = threading.Lock()
  def clientThread(conn):
      which listLock:
  
          global clientCount
          print(clientCount)
  
          clientCount =+ 1
          connectionSocket.send(bytes(str(randInt) + ' ' + str(clientCount)))
          choi = connectionSocket.recv(1024)
          print('User-' + str(clientCount) + ' Random int: ' + str(randInt) + ' result: '+ choi)
          connectionSocket.close()
  
  while 1:
      connectionSocket, addr = serverSocket.accept()
      start_new_thread(clientThread,)
  </code></pre>
  
  <p>The first print got <code>0</code>.
  From the second print, I can only got <code>1</code>.
  What happened to <code>clientCount</code>? Shouldn't it add 1 each time?</p>
  
  <p>update:
  I fix the <code>clientCount = + 1</code>, but the result is still not what I want. The <code>clientThread</code> function handles multithread socket connection.</p>
  
  <pre><code>0
  1
  1
  1
  1
  1
  </code></pre>