title: Make "python" run python3 at the prompt
body: <p>I have two python installations..</p>
  
  <p><code>python</code> --> <code>/Users/fraz/anaconda/bin/python</code> (python2.7)</p>
  
  <p><code>python3.7</code> --> <code>/usr/local/bin/python3.7</code></p>
  
  <p>Now.. I want reassign the commands. Such that
  <code>python</code> points to <code>python3.7</code> --> <code>/usr/local/bin/python3.7</code></p>
  
  <p>and <code>python2</code> points to <code>python2.7</code> <code>/Users/fraz/anaconda/bin/python</code></p>
  
  <p>How  do i do this reassignment?</p>