What are iterators in Python?

An iterator is an object.

It remembers its state i.e., where it is during iteration (see code below to see how)

__iter__() method initializes an iterator.

It has a __next__() method which returns the next item in iteration and points to the next element. Upon reaching the end of iterable object __next__() must return StopIteration exception.

It is also self-iterable.

Iterators are objects with which we can iterate over iterable objects like lists, strings, etc.

class ArrayList:

def __init__(self, number_list):

self.numbers = number_list

def __iter__(self):

self.pos = 0

return self

def __next__(self):

if(self.pos < len(self.numbers)):

self.pos += 1

return self.numbers[self.pos - 1]

else:

raise StopIteration

array_obj = ArrayList([1, 2, 3])

it = iter(array_obj)

print(next(it)) #output: 2

print(next(it)) #output: 3

print(next(it))

#Throws Exception

#Traceback (most recent call last):

#...

#StopIteration