title: Sort columns in pandas using custom order for unknown number of columns
body: <p>I have following columns in my pandas DataFrame</p>
  
  <pre><code>DB_0, ISBN_0, ISSN_0, Title_0, e-ISBN_0, e-ISSN_, DB_1, ISBN_1, ISSN_1, Title_1, e-ISBN_1, e-ISSN_1 .... DB_n, ISBN_n, ISSN_n, Title_n, e-ISBN_n, e-ISSN_n
  </code></pre>
  
  <p>I want to change it to custom order, some like this:</p>
  
  <pre><code>Title_0, DB_0, ISSN_0, e-ISSN_0, ISBN_0, e-ISBN_0, Title_1, DB_1, ISSN_1, e-ISSN_1, ISBN_1, e-ISBN_1, ..... Title_n, DB_n, ISSN_n, e-ISSN_n, ISBN_n, e-ISBN_n
  </code></pre>
  
  <p>How can I achieve this result?? I have tried everything etc but nothing works. Tried to search it on google but didn't find the answer. The problem is we don't know how many columns we will have at the end.</p>