title: strip in Python 3 is not "working"?
body: <p>I have the following <code>string</code>:</p>
  
  <pre><code>s = 'sd sdasd sas sas zxxx df xx de '
  </code></pre>
  
  <p>When I use
  <code>s.strip('x')</code>I get the following result:</p>
  
  <pre><code>'sd sdasd sas sas zxxx df xx de '
  </code></pre>
  
  <p>Why is <code>strip()</code> not removing all <code>'x'</code> characters?</p>