title: Problem using pandas.get_dummies for a binary feature that returns 3 columns one with a tabulation
body: <p>I'm working on a binary classification machine learning problem and I use pandas function get_dummies to encode my categorical data. The function works well with all my data but 2 columns where it returns 3 categories for each instead of 2. For instance: I have a feature called "classification" where the value is "ckd" and "notckd". The get_dummies function returns a dataframe with <strong>column1</strong>: <em>ckd</em>, <strong>column2</strong>: <em>ckd\t</em>, <strong>column3</strong>: <em>notckd</em>. I've checked whether there were any tabulations in my data with many methods and there was none. Also, the second column <strong>ckd\t</strong> is 0 everywhere.
  I can just drop these supplementary columns but I still want to figure out what causes this problem.
  Thanks for your help.</p>