title: find string with format '[number]' using regex
body: <p>I have a string in a django/python app and need to search it for every instance of <code>[x]</code>. This includes the brackets and x, where x is any number between 1 and several million. I then need to replace x with my own string.</p>
  
  <p>ie, <code>'Some string [3423] of words and numbers like 9898'</code> would turn into <code>'Some string [mycustomtext] of words and numbers like 9898'</code></p>
  
  <p>Note only the bracketed number was affected. I am not familiar with regex but think this will do it for me?</p>