title: how to install python2 packages via pip when I have both python2 and python3?
body: <p>Now </p>
  
  <blockquote>
    <p>pip -V</p>
  </blockquote>
  
  <p>shows that it's python3.5's pip.</p>
  
  <p>What to do if I want python2's package?</p>