What exactly are iterator, iterable, and iteration?

Question

What is the most basic definition of \"iterable\", \"iterator\" and \"iteration\" in Python?

I have read multiple definitions but I am unable to identify the exact m

Answer 1

An iterable is a object which has a __iter__() method. It can possibly iterated over several times, such as list()s and tuple()s.

An iterator is the object which iterates. It is returned by an __iter__() method, returns itself via its own __iter__() method and has a next() method (__next__() in 3.x).

Iteration is the process of calling this next() resp. __next__() until it raises StopIteration.

Example:

>>> a = [1, 2, 3] # iterable
>>> b1 = iter(a) # iterator 1
>>> b2 = iter(a) # iterator 2, independent of b1
>>> next(b1)
1
>>> next(b1)
2
>>> next(b2) # start over, as it is the first call to b2
1
>>> next(b1)
3
>>> next(b1)
Traceback (most recent call last):
  File "", line 1, in 
StopIteration
>>> b1 = iter(a) # new one, start over
>>> next(b1)
1