title: Python Pandas: How to unique strings in a column
body: <p>I have a table like this:</p>
  
  <pre><code>col1 col2
  ben US-US-Uk
  Man Uk-NL-DE
  bee CA-CO-MX-MX
  </code></pre>
  
  <p>how can I unique the values in col 2, which means have a table like this?</p>
  
  <pre><code>col1 col2
  ben US-Uk
  Man Uk-NL-DE
  bee CA-CO-MX
  </code></pre>
  
  <p>I have tried this :</p>
  
  <pre><code>a.cc.str.split('-').unique()
  </code></pre>
  
  <p>but get the following error:</p>
  
  <pre><code>TypeError: unhashable type: 'list'
  </code></pre>
  
  <p>Does anybody know how to do this?</p>