Python Coding challenge - Day 1291| What is the output of the following Python Code?

 

Code Explanation:

1. Creating a Class

class A:    items = []

- class A: defines a class named A.

- items = [] creates an empty list as a class attribute.

- This list belongs to the class and is shared by its instances unless an instance attribute shadows it.

Initial state:

[]

2. Defining the add() Method

def add(self, x):    self.items.append(x)

- self refers to the instance calling the method.

- x is the value passed to the method.

- self.items looks up the items attribute on the instance first, then on the class if no instance attribute exists.

- .append(x) adds the value to the list in place.

Because neither instance has its own items attribute yet, both initially access the same class-level list.

3. Creating Two Objects

a, b = A(), A()

This creates two separate instances of class A:

- a is the first object.

- b is the second object.

Although the objects are separate, they both refer to the same class-level items list.

Conceptually:

a ──┐

    ├──> shared items list: []

b ──┘

4. Adding an Element Through a

a.add(1)

- The method accesses the shared list.

- append(1) adds 1 to it.

List state:

[1]

Both a.items and b.items now refer to this same list.

5. Adding an Element Through b

b.add(2)

- b accesses the same shared list.

- append(2) adds 2 to it.

Updated list:

[1, 2]

The list is shared, so the change is visible through both objects.

6. Understanding the print() Statement

print(a.items, b.items)

- a.items refers to the shared list [1, 2].

- b.items refers to that same list [1, 2].

- print() displays both values.

Final Output

[1, 2] [1, 2]