How to get the data in flask from the HTML input with changing the url of website

I have a input box in HTML and what I want is to get the data that get input in that box when button is clicked. I know how to get data from the form

ex =  request.form['example'];

I want to get the data in flask just like above but for the input box which look like this -

<div class="form-inline" id="inputDiv">
      <center>
        <input class="form-group" id="msg-content" autocomplete="off" placeholder="Send a message" />
        <button class="btn btn-lg" onclick="sendMsg()" id="sendBtn"><span class="glyphicon glyphicon-send"></span></button>
      </center>
</div>