[Python] Python, linked list

Here is a question from leetcode:

Define a function, input the head node of a linked list, invert the linked list.

example:

• input: 1->2->3->4->5->NULL
• output: 5->4->3->2->1->NULL

​

Here is the official answer to it:

# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next

class Solution:
def reverseList(self, head: ListNode) -> ListNode:
cur , pre = head, None
while cur:
tmp = cur.next
cur.next = pre
pre = cur
cur = tmp
return pre


I want to ask what does the line while cur: mean? Does it transverse the whole linked list? I tried to replace it with while head:, why it doesn't work since cur == head?

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