What is the difference between an iterator and an iterable object?

An iterable object is an object from which an iterator can be obtained. It implements the __iter__() method, which returns an iterator.

An iterator is an object that provides access to the elements of a collection one at a time. It implements the __iter__() and __next__() methods. The __next__() method returns the next element in the iteration or raises a StopIteration exception when exhausted.

# Example of an iterable object (list)
my_list = [1, 2, 3]

# Getting an iterator from an iterable object
my_iterator = iter(my_list) # Calls my_list.__iter__()

# Using the iterator to get elements
print(next(my_iterator)) # Calls my_iterator.__next__()
print(next(my_iterator))
print(next(my_iterator))

# When trying to get the next element after exhaustion
try:
    print(next(my_iterator))
except StopIteration:
    print("Iteration finished")

Key difference: an iterable object provides an iterator, and an iterator provides elements.

Comparison:

Characteristic	Iterable Object	Iterator
Implements method	__iter__()	__iter__(), __next__()
Action	Returns an iterator	Returns the next element
State	Contains data	Contains current position
Reusability	Multiple iterators can be obtained	Single-use only