class RunLengthIterator:
   def __init__(self, s):
     self.output = []
     num = ""
     for i in s:
         if i.isalpha():
            self.output.append(int(num))
            self.output.append(i)
            num = ""
         else:
            num += i

   def next(self):
      if self.hasnext():
         count = self.output[0]
         letter = self.output[1]
         count -= 1
         if count > 0:
            self.output[0] -= 1
         else:
            self.output = self.output[2:]
         return letter

   def hasnext(self):
      if len(self.output) != 0:
         return True
      return False

s = "2b1a"
obj = RunLengthIterator(s)
print(obj.next())
print(obj.hasnext())
print(obj.next())
print(obj.next())
print(obj.hasnext())

"2b1a"
obj = RunLengthIterator(s)
obj.next()
obj.hasnext()
obj.next()
obj.next()
obj.hasnext()