title: Modify a python package, remove it and re-install it: why modifications are persistent?
body: <p>I am working in Windows.</p>
  
  <ul>
  <li>installed a python package with <strong>conda</strong> (Zipline, from the channel 'Quantopian'), in an environment:</li>
  </ul>
  
  <blockquote>
    <p><code>conda install -c Quantopian zipline</code></p>
  </blockquote>
  
  <ul>
  <li>modified code inside some .py files in the package. These .py file are in the package folder inside the environment folder.</li>
  <li>removed the package:</li>
  </ul>
  
  <blockquote>
    <p><code>conda remove zipline</code></p>
  </blockquote>
  
  <ul>
  <li>checked the package folder is not there anymore.</li>
  <li>reinstalled the package:</li>
  </ul>
  
  <blockquote>
    <p><code>conda install -c Quantopian zipline</code></p>
  </blockquote>
  
  <ul>
  <li>checked the .py files inside the package folders: the still retain the modifications I did.
  Why?</li>
  </ul>