title: Python equivalent to R 's factor data type
body: <p>I'm new in using Python as scientific language. </p>
  
  <p>I'm missing using an data type that informs me the data it self and the factors the data are in. (Specially for categorical data array. )</p>
  
  <p>I'm wondering if there's a <strong>lib</strong> or <strong>an array</strong> type in <code>scipy package</code> for this usage ?</p>