title: Change installed Python module in virtualenv
body: <p>I have a module installed using <code>pip</code> in a <code>virtualenv</code>. I want to experiment with a single change on one line of its code, and wonder if it will work by going straight to the source file and changing that line?</p>
  
  <p>If not, what is the easiest way to do so? Download the source, change it, and run <code>python setup.py install</code> inside the <code>virtualenv</code>? But would that install the module inside the <code>virtualenv</code>? And can I still remove it later using <code>pip</code> or I need to clean it up manually?</p>