title: Remove all non-numeric part but keep the coma in python
body: <p>lets say I have a a string such as :</p>
  
  <pre><code>line = "tree length for XI:      31.0215"
  </code></pre>
  
  <p>I would liek to only keep the <code>31.0215</code> part. 
  I tried:</p>
  
  <pre><code>print (re.sub("^[0-9]", "",line))
  </code></pre>
  
  <p>but it does not work, the "." is removed, does anyone have an idea? </p>