title: How do I check if any entry boxes are empty in Tkinter?
body: <p>I am making a GUI in Tkinter with Python 2.7. I have a frame with about 30 entry boxes among other things. I don't have access to the code right now, but is there a way to check if any or several of the boxes are empty so I can warn the user and ask them if they want to proceed?</p>
  
  <p>Is there a way to go through each of them with a 'for' loop and check the length of each entry. Or is there a command to check if any box is empty?</p>