title: re.sub replace spaces with comma
body: <p>I have a list of items which look like so:</p>
  
  <pre><code> 2.4       -2.0           4.3
  -6.0       12.5           1.0
  </code></pre>
  
  <p>What I would like is to remove all those spaces and replace them with "," (comma) except for the spaces in front of first numbers (they should be just deleted (the spaces) and not replaced with anything). So the upper string items should look like so, after replacement:</p>
  
  <pre><code>2.4,-2.0,4.3
  -6.0,12.5,1.0
  </code></pre>
  
  <p>Not like this:</p>
  
  <pre><code>,2.4,-2.0,4.3
  ,-6.0,12.5,1.0
  </code></pre>
  
  <p>Which is what the following code does:</p>
  
  <pre><code>newStrings = []
  for s in strings:
      newStrings.append(re.sub('\s+', ',', s))
  </code></pre>
  
  <p>What regular expression for re.sub should be used to achieve that?
  Thank you.</p>