Python Coding challenge - Day 1172| What is the output of the following Python Code?

 

Code Explanation:

🔹 Line 1: Import cached_property

from functools import cached_property

Imports the cached_property decorator.

👉 It works like a property, but once the value is calculated, Python stores (caches) it and reuses the same value on future accesses.

🔹 Line 2: Create Class

class A:

A class named A is created.

🔹 Line 3–5: Define Cached Property

@cached_property

def x(self):

    return []

This creates a property named:

x

Whenever a.x is accessed for the first time, Python executes:

return []

and stores that returned list inside the object.

🔹 Line 7: Create Object

a = A()

An object of class A is created.

Current state:

a

⚠️ x() has not run yet.

Because cached_property is lazy.

🔹 Line 9: Access a.x

a.x.append(1)

Before .append(1) runs, Python evaluates:

a.x

Since this is the first access:

Python executes:

return []

A new list is created:

[]

and cached.

🔹 Internal State After First Access

Python now stores:

a.x → []

Think of it like:

{

    "x": []

}

inside the object.

🔹 Line 9 Continues: Execute Append

a.x.append(1)

becomes:

[].append(1)

List changes from:

[]

to:

[1]

Now cached value is:

a.x → [1]

🔹 Line 11: Print a.x

print(a.x)

Python checks:

Has x already been cached?

✅ Yes

Therefore Python does NOT execute:

return []

again.

Instead it directly returns the cached list:

[1]

🔹 Line 12: Print Output

print([1])

Output:

[1]