non iterorators in python code example

Example 1: python defining the iterator protocol

class RangeTen:
  def __init__(self, *args): pass # optional
  
  def __iter__(self):
    '''Initialize the iterator.'''
    self.count = -1
    return self
  
  def __next__(self):
  	'''Called for each iteration. Raise StopIteration when done.'''
    if self.count < 9:
      self.count += 1
      return self.count

    raise StopIteration
    
for x in RangeTen():
  print(x) # 0, 1, ..., 9

Example 2: iterator in python

class PowTwo:
    """Class to implement an iterator
    of powers of two"""

    def __init__(self, max=0):
        self.max = max

    def __iter__(self):
        self.n = 0
        return self

    def __next__(self):
        if self.n <= self.max:
            result = 2 ** self.n
            self.n += 1
            return result
        else:
            raise StopIteration


# create an object
numbers = PowTwo(3)

# create an iterable from the object
i = iter(numbers)

# Using next to get to the next iterator element
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))