so what u have done here is created 3 copies of iterator and the zip's index recognises this thing as 3 separate iterables so the index would be the same for each iterable upon which the zipping has to be performed. hence u re getting the same variable of the iterator as the result. if u ve given like iter(s)*3 the zip's index would be updated(incremented) on proceeding to the succeeding iterable (making zip to believe u have like only one iterable so dont go look for the other one to zip instead increment your index to the next variable on the same iterable.