title: How to generate a sequence of numbers when encountered a value in python pandas dataframe
body: <p><a href="https://i.stack.imgur.com/f92mo.jpg" rel="nofollow noreferrer">sample and expected data</a></p>
  
  <p>The block one is current data and block 2 is the expected data that is, when i encounter 1 i need the next row to be incremented by one and for next country b same should happen</p>