title: Match first instance of digit by Regex in python
body: <p>I am new to regex and need to extract just the 'Chr' number by reading an entry at a time.</p>
  
  <p>For example, for the following data:</p>
  
  <pre><code>Chr6_clust92082
  Chr7_clust13
  Chr7_clust256
  Chr7_clust3678
  Chr7_clust42
  Chr7_clust5
  Chr7_clust130538
  </code></pre>
  
  <p>The first entry should return '6' because it is right after 'Chr' and before '_'. Please suggest the specific regex for it.</p>