title: Python regex:combining re pattern format with a variable
body: <p>I would like to combine a python variable and pattern. How can I do it?</p>
  
  <p>below is what I would like to do.</p>
  
  <pre><code>re.search(r'**some_variable+pattern**',str_for_pattern_match,flags)
  </code></pre>
  
  <p>Thanks for your help.</p>