Iterator

'''
Iterables are any object that, when the iter() method is called (implicitly or not), 
returns an iterator (an object with a __next__() method). Sometimes, these
objects can even be the same (as is the case with this example).
'''

'''
This class is an iterable class, because it contains an __iter__() method which
returns an iterator (in this case, itself). Each time the next() method is called,
a value is generated. These values are lazily loaded, like generators, but they
are stored in memory as part of a class instance attribute.
'''

class iterable:
    def __init__(self, i, n):
        self.i = i
        self.n = n
        
    def __iter__(self): # <-- makes this an iterable, and returns an iterator (itself)
        return self
        
    def __next__(self):
        if self.i < self.n:
            tmp = self.i
            self.i += 1
            return tmp**2
        else:
            raise StopIteration
            

y = iterable(1, 10)

for j in y:
    # print(y.i)    <-- this line prints the value of i when the function returns
    print(j)