title: module not found on ipython notebook
body: <p>I have an ipython notebook which starts with </p>
  
  <pre><code>import sklearn
  </code></pre>
  
  <p>When I run it, I get :</p>
  
  <pre><code>ImportError: No module named sklearn
  </code></pre>
  
  <p>indeed if I run the following snippet on the notebook, it's not showing scikit_learn:</p>
  
  <pre><code>import pip
  installed_packages = pip.get_installed_distributions()
  installed_packages_list = sorted(["%s==%s" % (i.key, i.version)
       for i in installed_packages])
  print installed_packages_list
  </code></pre>
  
  <p>However when I run the snippet from command line, scikit_learn is in the list.</p>
  
  <p>I thought of a version problem (module installed for one version and not on the other one), bur both on notebook and command line, sys.version give 2.7.5</p>
  
  <p>Any idea about the issue here ?</p>
  
  <p>Following cel's comments:</p>
  
  <pre><code>ipython -c "import sys; print(sys.executable)" 
  </code></pre>
  
  <p>outputs /usr/bin/python (and so does running <code>import sys; print(sys.executable)</code> directly in the notebook)</p>
  
  <p>Then, <code>/usr/bin/python -m pip install scikit-learn</code>
  outputs: Requirement already satisfied (use --upgrade to upgrade): scikit-learn in /Users/MyUserName</p>