title: ROS2 + Qt: any good solution?
body: <p>I've built a Qt GUI in python from code (not from the Qt editor, so I don't use qml files).
  I want it to be able to subscribe to ROS2 topics and update the GUI according to the messages received, and publish data when a button is clicked.
  The problem is that Qt requires <code>app.exec()</code>, and ROS requires <code>node.spin()</code> to be run, both of which are infinite loops.
  There seem to be some tutorials online for ROS + Qt, but all of them are focused on ROS1.
  I can't find any example code for ROS2 + Qt.</p>
  
  <p>How can I integrate my Qt GUI with ROS2?</p>