title: Why does anaconda download again packages that I already have when creating a new environment?
body: <p>I have used anaconda3 for a few projects recently, and every time I create a virtual environment for a project, it seems that anaconda is re-downloading the same packages (pytorch, for instance).</p>
  <p>Have I misconfigured something or this behavior is OK?</p>
  <p>for clerification, I am doing the Stanford CS224n course and for the assignments I use:</p>
  <pre><code>conda env create --file env.yml
  </code></pre>
  <p>Where env.yml is of the form:</p>
  <pre class="lang-yml prettyprint-override"><code>name: local_nmt
  channels:
    - pytorch
    - defaults
  dependencies:
    - python=3.5
    - numpy
    - scipy
    - tqdm
    - docopt
    - pytorch
    - nltk
    - torchvision
  </code></pre>
  <p>I couldn't fine an explanation in the anaconda documentation.
  Thanks in advance!</p>