Python Coding challenge - Day 484| What is the output of the following Python Code?

 

Code Explanation:

Function Definition

def append_to_list(val, list=[]):

What Happens:

A function named append_to_list is defined.

It takes two parameters:

val: the value to be added to a list.

list: an optional parameter, with a default value of an empty list [].

Append Value to List

    list.append(val)

What Happens:

The method append(val) adds the value val to the end of the list.

If no custom list was passed, it uses the shared default list, which keeps getting modified across function calls.

Return the Modified List

    return list

 What Happens:

The updated list is returned as the output of the function.

First Function Call

print(append_to_list(1))

What Happens:

No list is passed, so it uses the default list: [].

1 is appended → list becomes [1].

The default list is now modified and becomes [1].

Output:

[1]

Second Function Call

print(append_to_list(2, []))

What Happens:

A new empty list [] is passed.

2 is appended to this new list → list becomes [2].

The default list ([1]) is not affected here.

Output:

[2]

Third Function Call

print(append_to_list(3))

What Happens:

No list is passed again, so it uses the modified default list from the first call, which is now [1].

3 is appended → list becomes [1, 3].

Output:

[1, 3]

Final Output Summary

[1]

[2]

[1, 3]