title: Substitute multiple whitespace with single whitespace in Python
body: <p>I have this string:</p>
  
  <pre><code>mystring = 'Here is  some   text   I      wrote   '
  </code></pre>
  
  <p>How can I substitute the double, triple (...) whitespace chracters with a single space, so that I get:</p>
  
  <pre><code>mystring = 'Here is some text I wrote'
  </code></pre>