Implement an iterator

Reference

https://treyhunner.com/2018/06/how-to-make-an-iterator-in-python/

Making an iterator: the object-oriented way

class MyIteroar:
    def __init__(self, a):
        self.i =-1
        self.a = a
    def __iter__(self):
        return self
    def __next__(self):
        if self.a>=len(self.a):
             raise StopIteration
        self.i +=1
        return self.a[self.i]

by using a generator

def my_iterator(a):
    for item in a:
        yield item