title: algorithm to find derivative
body: <p>I'm writing program in Python and I need to find the derivative of a function (a function expressed as string).</p>
  
  <ul>
  <li>For example: <code>x^2+3*x</code></li>
  <li>Its derivative is: <code>2*x+3</code></li>
  </ul>
  
  <p>Are there any scripts available, or is there something helpful you can tell me?</p>