Python Coding challenge - Day 592| What is the output of the following Python Code?

 

Code Explanation:

Line 1: def pack(f):

Defines a function pack that takes another function f as an argument.

This is a higher-order function (a function that works with other functions).

Line 2–3: Inner Function wrap(x) and Return

def wrap(x): return (f(x), x)

return wrap

wrap(x) is a nested function that:

Calls f(x) and returns a tuple: (f(x), x)

pack(f) finally returns this wrap function.

Purpose: It wraps any function so that calling it returns both the result and the original input.

Line 4: Using Decorator @pack

@pack

def square(x): return x ** 2

This is equivalent to:

def square(x): return x ** 2

square = pack(square)

So now square is actually the wrap function returned by pack.

Meaning:

square(3) → (square(3), 3) → ((3**2), 3) → (9, 3)

 Line 5: Function Call and Indexing

print(square(3)[1])

square(3) now returns (9, 3)

square(3)[1] accesses the second element of the tuple, which is 3.

print(...) prints that value to the screen.

Final Output:

3

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