title: How to update datetime regularly?
body: <p>I want to print out the datetime every second. When I ran</p>
  <pre><code>import time, datetime
  
  t0 = time.time()
  
  while True:
      print (time.strftime(&quot;%H:%M:%S&quot;,time.localtime(t0)))
      time.sleep(1)
  </code></pre>
  <p>I expected to see this</p>
  <pre><code>20:58:30
  20:58:31
  20:58:32
  20:58:33
  20:58:34
  </code></pre>
  <p>etc. But I got this instead:</p>
  <pre><code>20:58:30
  20:58:30
  20:58:30
  20:58:30
  20:58:30
  </code></pre>
  <p>How do I do it right?</p>