title: Creating a virtualenv with preinstalled packages as in requirements.txt
body: <p>Creating a virtualenv will create a virtual python environment with preinstalled pip, setuptools and wheels.</p>
  
  <p>Is there a way to specify what packages to pre-install in that virtualenv apart from those 3 default ones? Either with CLI arguments, a file, or environment variables of some sort. </p>
  
  <p>I.e. is there something along the lines of <code>virtualenv venv &amp;&amp; venv/bin/pip install -r requirements.txt</code> which can be run in one command?</p>