the object variable in link list reverse codes - variables

Question

Hi this is a link list reverse code. Anyone can help me understand that the differecen between r = Solution().reverseList(n1) and r = Solution().reverseList(ListNode(1)).
I wonder why the output which is [1] and [3,2,1] respectively and what is the purpose of to assign the ListNode object to a variable.
class Solution(object):
def reverseList(self, head):
"""
:type head: ListNode
:rtype: ListNode
"""
#if not head:
# return None
prev = head
curr = prev.next
while curr:
next =curr.next
curr.next = prev
prev = curr
curr = next
head.next = None
return prev
class ListNode(object):
def __init__(self,x):
self.val = x
self.next = None
def to_list(self):
return[self.val] + self.next.to_list() if self.next else [self.val]
if __name__ == "__main__":
n1 = ListNode(1)
n2 = ListNode(2)
n3 = ListNode(3)
n1.next = n2
n2.next = n3
r = Solution().reverseList(n1)
print r.to_list()
#assert r.to_list() == [3,2,1]

Answer 1

I understood now.
ListNode(1) has no "next" set, so it will forever return 1 as it's list, whereas n1 starts the same way (as just node of 1), but the "next" attribute is set to node of 2 whose "next" is set to node of 3, so n1 carries all of this information with it, and ListNode(1) does not.
welcome any comments.