title: Shorter way to check if a string is not isdigit()
body: <p>For the sake of learning, is there a shorter way to do:
  <code>if string.isdigit() == False :</code></p>
  
  <p>I tried:
  <code>if !string.isdigit() :</code> and <code>if !(string.isdigit()) :</code> which both didn't work.</p>