title: eliminate space between comma and thousands digits in python regex
body: <p>I am trying to fix some data. It is almost 6 million words but I've found that some of it has been separated by commas then a space in numbers. For instance:</p>
  
  <pre><code>1, 000, 000 cases were produced of this, however, that is not important.
  </code></pre>
  
  <p>I was using:</p>
  
  <pre><code>changed = re.sub(r', \d{3}', r'\d{3}',original.strip())
  </code></pre>
  
  <p>but that changes it to:</p>
  
  <pre><code>1,\d{3},\d{3} cases were produced of this, however, that is not important.
  </code></pre>
  
  <p>so it recognizes what needs to be changed, but not what it needs to be changed to</p>