Python Coding challenge - Day 726| What is the output of the following Python Code?

 

Code Explanation:

1) nums = [1, 2, 3, 4] — create the original list

A list object is allocated containing the integers 1, 2, 3, 4.

Variable nums references (points to) that list.

2) ref = nums — create an alias (another name)

ref is not a new list; it points to the same list object as nums.

Any mutation through ref or nums will affect the same underlying list.

3) copy = nums[:] — make a shallow copy using slicing

nums[:] creates a new list with the same elements.

copy references this new list.

Now you have two different list objects: the original (nums) and the copy (copy).

4) ref[0] = 99 — mutate the list via the alias

This changes index 0 of the list that ref points to.

Because ref and nums reference the same object, nums[0] is also changed.

After this line: nums (and ref) is [99, 2, 3, 4].

5) copy[1] = 100 — mutate the copied list

This changes index 1 on the separate copy list only.

The original nums is unaffected by changes to copy.

After this line: copy is [1, 100, 3, 4].

6) print(nums, copy) — show both lists

Prints the current state of both lists:

[99, 2, 3, 4] [1, 100, 3, 4]

Final Output:

[99, 2, 3, 4] [1, 100, 3, 4]

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