pip or pip3 to install packages for Python 3? : <p>I have a Macbook with OS X El Captain. I think that <code>Python 2.7</code> comes preinstalled on it. However, I installed <code>Python 3.5</code> too. When I started using <code>Python 3</code>, I read that if I want to install a package, I should type:</p>

<pre><code>pip3 install some_package
</code></pre>

<p>Anyway, now when I use</p>

<pre><code>pip install some_package
</code></pre>

<p>I get <code>some_package</code> installed for <code>Python 3</code>. I mean I can import it and use it without problems. Moreover, when I type just <code>pip3</code> in <code>Terminal</code>, I got this message about the usage:</p>

<pre><code>Usage:   
  pip &lt;command&gt; [options]
</code></pre>

<p>which is the same message I get when I type just <code>pip</code>.</p>

<p>Does it mean that in previos versions, things were different, and now <code>pip</code> and <code>pip3</code> can be used interchangeably? If so, and for the sake of argument, how can I install packages for <code>Python 2</code> instead of <code>Python 3</code>?</p>
