Infinity iterators with itertools module

[maina]

An infinite iterator is any iterator that can go on yielding values indefinitely. This means that the iterator will never raise the StopIteration exception because there will always be a value to be yielded.

The itertools module provides three functions to create infinity iterators:

• cycle
  
• count
  
• repeat
  

The cycle() function creates an iterator that yields the elements of the target iterable in a cyclic manner. When the end is reached, the iteration moves back to the start of iterable.

import itertools

data = ['Python', 'Java', 'Kotlin']

obj = itertools.cycle(data)

print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))

Output:
Python
Java
Kotlin
Python
Java
Kotlin
Python

The itertools.count() generates infinite numbers given a starting point and the skip/step value.

import itertools

nums = itertools.count(0, 20)

print(next(nums))
print(next(nums))
print(next(nums))
print(next(nums))
print(next(nums))
print(next(nums))

#this can go on indefinitely

Output:
0
20
40
60
80
100

Finally, the itertools.repeat() function repeats a value for a given number of times or indefinitely if the number of times is not given.

import itertools

obj = itertools.repeat('Python')

print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))
print(next(obj))

#this can go on indefinitely

Output:
Python
Python
Python
Python
Python
Python