title: What does sys.exit really do with multiple threads?
body: <p>I was really confused by sys.exit() in python.
  In <a href="https://docs.python.org/2/library/sys.html" rel="noreferrer">python documentation</a>, it says "Exit from Python"; does that mean when <code>sys.exit()</code> is called in a python program, the process will exit? If so, the code below shows a different result:</p>
  
  <pre><code>import sys
  import time
  import threading
  
  def threadrun():
      while(True):
          time.sleep(1)
  
  if __name__=="__main__":
      t=threading.Thread(target=threadrun)
      t.start()
      sys.exit()
  </code></pre>
  
  <p>Launching this program in linux, result was not the expected one as python documentation says but still run in the system, so what does <code>sys.exit()</code> really do?</p>