title: How to check if the name doesn't contain two dots going together with regex?
body: <p>I have a string, and I want to check if this name doesn't contain exactly 2 dots combined:</p>
  
  <pre><code>"p.a.s@siv" - false 
  "p..as@siv" - true 
  "p...as@siv" - false
  </code></pre>
  
  <p>Is it possible to check this using regular expressions and python?</p>
  
  <p>I found here and tried this pattern: </p>
  
  <pre><code>$pattern = '/^([^\.]|([^\.])\.[^\.])*$/';
  </code></pre>
  
  <p>but it doesn't work properly in first and third case. As I understood, it means that we check a symbol and it's not dot OR we check the symbol and this is not dot and the next following symbol is a dot and the next after next is not a dot.</p>