Python Iterators

An iterator is an object that allows iteration over a sequence of elements. It implements the iterator protocol, which consists of the __iter__() and __next__() methods.

1. Creating an Iterator

To create an iterator in Python, you can use a class that implements the iterator protocol.

class MyIterator:
    def __iter__(self):
        self.n = 1
        return self

    def __next__(self):
        if self.n <= 5:
            result = self.n
            self.n += 1
            return result
        else:
            raise StopIteration

my_iter = MyIterator()
my_iter_iter = iter(my_iter)
print(next(my_iter_iter))  # Output: 1
print(next(my_iter_iter))  # Output: 2
print(next(my_iter_iter))  # Output: 3
print(next(my_iter_iter))  # Output: 4
print(next(my_iter_iter))  # Output: 5
# print(next(my_iter_iter))  # Raises StopIteration

2. Using Iterators with Iterable Objects

Many built-in Python objects are iterable and can be used with iterators.

my_list = [1, 2, 3, 4, 5]
my_list_iter = iter(my_list)
print(next(my_list_iter))  # Output: 1
print(next(my_list_iter))  # Output: 2
print(next(my_list_iter))  # Output: 3

3. Using Iterators in Loops

Iterators are commonly used in loops to iterate over elements of a sequence.

my_list = [1, 2, 3, 4, 5]
for item in my_list:
    print(item)

Conclusion

Iterators are essential for iterating over sequences of elements in Python. Understanding how to create and use iterators is fundamental for working with iterable objects efficiently.