title: How to use python variable in os.system?
body: <p>I am creating small console script in python, and I will like to put cowsay command in it, but cow says name of the variable, where the string is, not the string inside the variable.
  How I can get the cow to say string inside the variable?</p>
  
  <pre><code>if (command == 'cow'):
      word = raw_input('What does the cow say?  ')
      os.system('cowsay word')
  </code></pre>