Python Coding challenge - Day 693| What is the output of the following Python Code?

 

Code Explanation:

1) Function Definition

def f(a, L=[]):

Defines a function f with:

A required argument a.

An optional argument L with a default value of an empty list [].

Important: Default values are evaluated only once at function definition time, not each time the function is called.

So the same list object is reused across calls unless a new list is explicitly passed.

2) Function Body

L.append(a)

return L

The function appends the argument a into the list L.

Then returns that (possibly shared) list.

3) First Call

print(f(1))

No second argument → uses the default list [].

L = [], then 1 is appended → L = [1].

Returns [1].

Output so far:

[1]

4) Second Call

print(f(2, []))

Here we explicitly pass a new empty list [].

So L is not the shared default; it’s a fresh list.

2 is appended → L = [2].

Returns [2].

Output :

[1]

[2]

5) Third Call

print(f(3))

No second argument again → uses the same default list created in the first call (already contains [1]).

3 is appended → L = [1, 3].

Returns [1, 3].

Final Output:

[1]

[2]

[1, 3]

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