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1. Create Class & Object2. Instance vs Class Variables3. Constructors in Python Classes4. Single Inheritance5. Multiple Inheritance6. Multilevel Inheritance7. Polymorphism with Methods8. Method Overloading Simulation9. Encapsulation with Getters/Setters10. Abstraction with ABC11. Operator Overloading12. Custom Iterator13. Class Methods14. Static Methods15. Composition Example16. Aggregation Example17. Private Variables18. Magic Methods Overview19. Object Cloning20. Custom Exceptions21. Class Decorator22. Prototype Pattern23. Singleton Pattern24. MRO (Method Resolution Order) Demo25. Polymorphism (Duck Typing)

Custom Iterator in Python

Implement a class that can be iterated over using __iter__ and __next__.

IntermediateObject-Oriented ProgramsExample 12 of 25
custom-iterator.py
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1# Program to implement a custom iterator
2

3class Countdown:
4    def __init__(self, start):
5        self.current = start
6

7    def __iter__(self):
8        return self
9

10    def __next__(self):
11        if self.current <= 0:
12            raise StopIteration
13        value = self.current
14        self.current -= 1
15        return value
16

17for num in Countdown(3):
18    print(num)

Output

3
2
1

What's going on

By defining __iter__ and __next__, Countdown becomes an iterator usable in for-loops.

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