title: How to update an existing Conda environment with a .yml file
body: <p>How can a pre-existing conda environment be updated with another .yml file. This is extremely helpful when working on projects that have multiple requirement files, i.e. <code>base.yml, local.yml, production.yml</code>, etc.</p>
  
  <p>For example, below is a <code>base.yml</code> file has conda-forge, conda, and pip packages:</p>
  
  <p>base.yml</p>
  
  <pre><code>name: myenv
  channels:
    - conda-forge
  dependencies:
    - django=1.10.5
    - pip:
      - django-crispy-forms==1.6.1
  </code></pre>
  
  <p>The actual environment is created with:
  <code>conda env create -f base.yml</code>.</p>
  
  <p>Later on, additional packages need to be added to <code>base.yml</code>. Another file, say <code>local.yml</code>, needs to import those updates.</p>
  
  <p>Previous attempts to accomplish this include:</p>
  
  <p>creating a <code>local.yml</code> file with an import definition:</p>
  
  <pre><code>channels:
  
  dependencies:
    - pip:
      - boto3==1.4.4
  imports:
    - requirements/base. 
  </code></pre>
  
  <p>And then run the command:
  <code>conda install -f local.yml</code>. </p>
  
  <p>This does not work. Any thoughts?</p>