title: regex to extract mentions in Twitter
body: <p>I need to write a regex in python to extract mentions from Tweets.</p>
  
  <p>My attempt:</p>
  
  <pre><code>regex=re.compile(r"(?&lt;=^|(?&lt;=[^a-zA-Z0-9-_\.]))@([A-Za-z]+[A-Za-z0-9]+)")
  </code></pre>
  
  <p>It works fine for any mention like @mickey
  However, in mentions with underscores like @mickey_mouse, it only extracts @mickey.</p>
  
  <p>How can I modify the regex for it to work in both cases?</p>
  
  <p>Thank you </p>