An iterator is a collection of values that may be counted.
An iterator is a type of object that can be iterated over, which means you can go over all of the values.
An iterator is a Python object that implements the iterator protocol, which includes the methods __iter__(>
and __next__ (>
.
Iterable vs. Iterator
Iterable objects include lists, tuples, dictionaries, and sets. They are iterable containers from which an iterator can be obtained.
The iter(>
method on all of these types is used to get an iterator:
Example
Return an iterator from a tuple, and print each value:
mytuple = ("apple", "mango", "orange">
myiterator = iter(mytuple>
print(next(myiterator>
>
print(next(myiterator>
>
print(next(myiterator>
>
Output:
Try it here
Example
Strings are also iterable objects, containing a sequence of characters:
mystr = "orange"
myitr = iter(mystr>
print(next(myitr>
>
print(next(myitr>
>
print(next(myitr>
>
print(next(myitr>
>
print(next(myitr>
>
print(next(myitr>
>
Output:
Try it here
You must implement the methods __iter__(>
and __next__(>
in your object/class to make it an iterator.
All classes have a function called __init__(>
, which allows you to do some initialising while the object is being formed, as you learned in the Python Classes/Objects chapter.
You can execute actions (initialising, etc.>
with the __iter__(>
method, but you must always return the iterator object itself.
You can also perform operations with the __next__(>
method, which must return the next item in the series.
class MyNumbers:
def __iter__(self>
:
self.b = 2
return self
def __next__(self>
:
x = self.b
self.b += 2
return x
myclass = MyNumbers(>
myiterator = iter(myclass>
print(next(myiterator>
>
print(next(myiterator>
>
print(next(myiterator>
>
print(next(myiterator>
>
print(next(myiterator>
>
Output:
Try it here
