Python Coding challenge - Day 1007| What is the output of the following Python Code?

 

Code Explanation:

1. Defining the class

class One:

This line defines a class named One.

The goal of this class is to allow only one object to be created.

2. Class variable to store the instance

    _obj = None

_obj is a class variable.

It will store the single instance of the class.

Initially, it is set to None (meaning no object exists yet).

3. Overriding the __new__ method

    def __new__(cls):

__new__ is a special method responsible for creating objects.

It runs before __init__.

cls refers to the class (One), not an instance.

4. Checking if an object already exists

        if not cls._obj:

This checks whether _obj is still None.

If True, it means no instance has been created yet.

5. Creating the object

            cls._obj = super().__new__(cls)

super().__new__(cls) creates a new object of class One.

The newly created object is stored in cls._obj.

This step happens only once.

6. Returning the same object every time

        return cls._obj

Whether a new object was created or not, this line always returns the same instance.

So every call to One() gives back the same object.

7. Creating the first reference

a = One()

Since _obj is None, a new object is created.

a now refers to that single instance.

8. Creating the second reference

b = One()

_obj already exists.

No new object is created.

b refers to the same object as a.

9. Identity comparison

print(a is b)

is checks whether both variables point to the same object in memory.

Since a and b refer to the same instance, the result is:

True

Final Output

True

400 Days Python Coding Challenges with Explanation