title: Most efficient way to un-dummy variables in Pandas DF
body: <p>So in the screenshot below, we have 3 different energy sites, ID01, ID18, and ID31. They're in a dummy variable type of format, and for visualization purposes I want to just create a column named 'Sites' that I can use. You'll see the loop I quickly made to do this, but it seems super inefficient. Any pointers on how to achieve this in the fastest way possible?</p>
  
  <p><img src="https://i.stack.imgur.com/lBYmJ.png" alt="Screenshot"></p>