title: Check if a string contains a number
body: <p>Most of the questions I've found are biased on the fact they're looking for letters in their numbers, whereas I'm looking for numbers in what I'd like to be a numberless string.
  I need to enter a string and check to see if it contains any numbers and if it does reject it.</p>
  
  <p>The function <code>isdigit()</code> only returns <code>True</code> if ALL of the characters are numbers. I just want to see if the user has entered a number so a sentence like <code>"I own 1 dog"</code> or something.</p>
  
  <p>Any ideas?</p>