[Python] What is the difference when assigning an object like a LinkedList to a variable...

I was working on this problem from HackerRank trying to insert an element at the tail of a linked list and I have to return the head of the node.

def insertNodeAtTail(head, data):
if head is None:
head = SinglyLinkedListNode(data)
return head
current_head = head
while current_head.next:
current_head = current_head.next
current_head.next = SinglyLinkedListNode(data)
return head


SinglyLinkedListNode is a class for creating nodes with 2 methods: data which gives value to the node, and next which allows us to move on to the next node.

The code above works but my understanding is, if we mess or tweak with current_head, the changes will appear on head too (because that's how assigning works in Python). But the code is working perfectly. If I use return current_head, the answer is wrong. I did something similar such as

a = [1,2,3,4,5,6]
b = a
for i in range(5):
b.append(i)


And both array a and array b are identical and prints [1,2,3,4,5,6,0,1,2,3,4]. I'd appreciate any help I can get please. This inconsistency is messing with my head because the idea for inserting at the end of the tail is clearly easy but I keep getting worried about having to return the head of the node (and I can't do that if I keep misunderstanding whether I am changing anything to the LL).

Thank you in advance!

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