title: how to specify python version in Jupyter notebook
body: <p>I need to run python 3.5 but my Jupyter notebook runs 3.6 instead.
  It seems I can only specify either python 3 or python 2.</p>
  
  <p>How do I specify it to run 3.5, not 3.6?</p>
  
  <p>Some context: I'm trying to solve this error.</p>
  
  <pre><code>/home/duhduh/anaconda3/lib/python3.6/importlib/_bootstrap.py:219: RuntimeWarning: compiletime version 3.5 of module 'tensorflow.python.framework.fast_tensor_util' does not match runtime version 3.6
    return f(*args, **kwds)
  </code></pre>