Python Iterators

Iterators:

• Collection data types always an important concept in Python.
• We iterate the data of collection object using iterators
• Iterator in Python is simply an object that can be iterated upon.
• An object which will return data, one element at a time.
• The two methods __iter__() and __next__() are used to iterate an object.
• An object is called iterable if we can get an iterator from it. Most of built-in containers in Python like: list, tuple, string etc. are iterables.

my_list = [4, 7, 0, 3]

my_iter = iter(my_list)

print(next(my_iter))
print(next(my_iter))

print(my_iter.__next__())
print(my_iter.__next__())

next(my_iter)

We can easily iterate the collection object elements using for loop as follows:

for element in iterable:
    # do something with element

It is actually implemented as:

# create an iterator object from that iterable
iter_obj = iter(iterable)

# infinite loop
while True:
    try:
        # get the next item
        element = next(iter_obj)
        # do something with element
    except StopIteration:
        # if StopIteration is raised, break from loop
        break

• So internally, the for loop creates an iterator object, iter_obj by calling iter() on the iterable.
• Ironically, this for loop is actually an infinite while loop.