iterator protocol 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

# define a list
my_list = [4, 7, 0, 3]

# get an iterator using iter()
my_iter = iter(my_list)

# iterate through it using next()

# Output: 4
print(next(my_iter))

# Output: 7
print(next(my_iter))

# next(obj) is same as obj.__next__()

# Output: 0
print(my_iter.__next__())

# Output: 3
print(my_iter.__next__())

# This will raise error, no items left
next(my_iter)