title: how to check which version of nltk, scikit learn installed?
body: <p>In shell script I am checking whether this packages are installed or not, if not installed then install it. So withing shell script:</p>
  
  <pre><code>import nltk
  echo nltk.__version__
  </code></pre>
  
  <p>but it stops shell script at <code>import</code> line</p>
  
  <p>in linux terminal tried to see in this manner:</p>
  
  <pre><code>which nltk
  </code></pre>
  
  <p>which gives nothing thought it is installed.</p>
  
  <p>Is there any other way to verify this package installation in shell script, if not installed, also install it.</p>