Python Iterators

Iterators helps to iterate the iterable objects like list, tuple, set and dict in python. We can create custom iterator for the python functions

Iterators

Two function - iter and next helps to achieve the iterate over the given data in python like the below example

num_list = [10, 20, 30, 40, 50]

#Make the num list iterable
iter_num_list = iter(num_list)

while num_list:
    try:
        print(next(iter_num_list))
    #No more elements raises stop iteration exception
    except StopIteration:
        break

Output

10
20
30
40
50

Custom Iterators

Implementation of custom iterators for our function is very easier. With the help of __iter__ and __next__ methods, we can build the custom iterators like the below example

#Custom Iterator 
class TenMultipler:
    def __init__(self, multiple, max_limit):
        self.multiple = multiple
        self.max_limit = max_limit

    def __iter__(self):
        self.start = self.multiple
        return self

    def __next__(self):
        result = self.multiple * 10
        if result <= self.max_limit:
            self.multiple = self.start + self.multiple
            return result
        else:
            raise StopIteration

tenMultipler = TenMultipler(2, 100)
iter_tenMultipler = iter(tenMultipler)
while iter_tenMultipler:
    try:
        print(next(iter_tenMultipler))
    except:
        print("Max limit reached - Iteration stopped")
        break

Output

20
40
60
80
100
Max limit reached - Iteration stopped