title: How to check if two consecutive digits are the same in python
body: <p>I found this practice today:</p>
  
  <p>Detect whether a check number is valid or not. The check number must have 10 digits, can not have 2 or more zeros followed, nor three or more digits other than zero followed</p>
  
  <p>I've able to complete the first part with this code:</p>
  
  <pre><code>num_chk=input('Enter chk number: ')
  
  if (len(num_chk) == 10):
      print('valid')
  else:
      print('not valid')
  </code></pre>
  
  <p>any thoughts on how to create the logic to check if the check number has 2 consecutive 0.</p>
  
  <p>thanks</p>