Python Coding challenge - Day 951| What is the output of the following Python Code?

 Code Explanation:

1. Defining the Outer Function

def outer(lst=[]):

A function named outer is defined.

It has a parameter lst with a default value of an empty list [].

This default list is created once at function definition time, not each time outer() is called.

2. Defining the Inner Function

    def inner():

        lst.append(len(lst))

        return lst

inner is defined inside outer.

It captures lst from the enclosing scope (closure).

Each call:

Appends the current length of lst to lst.

Returns the modified list.

3. Returning the Inner Function

    return inner

outer returns the function inner.

The returned function keeps a reference to the same lst.

4. Creating Two Functions

f = outer()

g = outer()

outer() is called twice.

But since lst is a shared default argument, both f and g refer to the same list object.

So:

f.lst  → same list

g.lst  → same list

5. Calling the Functions

print(f(), g())

Let’s evaluate:

▶ f():

Initial lst = []

len(lst) = 0 → append 0

lst = [0]

Returns [0]

▶ g():

Uses the same list

Now lst = [0]

len(lst) = 1 → append 1

lst = [0, 1]

Returns [0, 1]

6. Final Output

[0] [0, 1]

Final Answer

✔ Output:

[0] [0, 1]

300 Days Python Coding Challenges with Explanation