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

Other people already explained comprehensively, what is iterable and iterator, so I will try to do the same thing with generators.

IMHO the main problem for understanding generators is a confusing use of the word “generator”, because this word is used in 2 different meanings:

1. as a tool for creating (generating) iterators,
   • in the form of a function returning an iterator (i.e. with the yield statement(s) in its body),
   • in the form of a generator expression
2. as a result of the use of that tool, i.e. the resulting iterator.
   (In this meaning a generator is a special form of an iterator — the word “generator” points out how this iterator was created.)

---

Generator as a tool of the 1^st type:

In[2]: def my_generator():
  ...:     yield 100
  ...:     yield 200

In[3]: my_generator

Out[3]: 

In[4]: type(my_generator)

Out[4]: function

Generator as a result (i.e. an iterator) of the use of this tool:

In[5]: my_iterator = my_generator()
In[6]: my_iterator

Out[6]: 

In[7]: type(my_iterator)

Out[7]: generator

---

Generator as a tool of the 2^nd type — indistinguishable from the resulting iterator of this tool:

In[8]: my_gen_expression = (2 * i for i in (10, 20))
In[9]: my_gen_expression

Out[9]:  at 0x000000000542C048>

In[10]: type(my_gen_expression)

Out[10]: generator