title: How to unistall python3.5 and re-install python3.7
body: <p>I am on a google compute engine Debian instance. It currently has python3.5 but not python3.7. How would I uninstall python3.5 and re-install python3.7? Here is an example:</p>
  
  <pre><code>david@instance-py3:~$ python3
  Python 3.5.3 (default, Jan 19 2017, 14:11:04) 
  [GCC 6.3.0 20170118] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; 
  david@instance-py3:~$ python3.7
  -bash: python3.7: command not found
  </code></pre>
  
  <p>I don't want to have both, but uninstall python3.5 before proceeding.</p>