An iterator is an object which implements the iterator protocol, which consist of the methods __iter__() and __next__()
Iterator vs Iterable
Lists, tuples, dictionaries, and sets are all iterable objects. They are iterable containers which you can get an iterator from.
All these objects have a iter() method which is used to get an iterator:
Example 1:
mytuple = ("apple", "banana", "cherry")
myit = iter(mytuple)
print(next(myit))
print(next(myit))
print(next(myit))
Example 2: Build custom an Iterator
class PowTwo:
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
numbers = PowTwo(3)
i = iter(numbers) # iterator
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))