在Python中迭代反转链表后无法分配head

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def reverseLinkedList(head):
    if head is None:
        return None
    if head.next is None:
        return head

    prev = None
    curr = head
    next = None

    while curr is not None:
        next = curr.next
        curr.next = prev
        prev = curr
        curr = next

    return prev

# 示例用法
# 创建链表：1 -> 2 -> 3 -> 4 -> 5
head = ListNode(1)
head.next = ListNode(2)
head.next.next = ListNode(3)
head.next.next.next = ListNode(4)
head.next.next.next.next = ListNode(5)

# 反转链表
new_head = reverseLinkedList(head)

# 输出反转后的链表：5 -> 4 -> 3 -> 2 -> 1
while new_head is not None:
    print(new_head.val)
    new_head = new_head.next