请用python代码实现链表结构，并用链表实现成对调换，例如：1->2->3->4 转换成 2->1->4->3

好的，以下是Python实现链表的代码：

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

class LinkedList:
    def __init__(self):
        self.head = None
    
    def addNode(self, val):
        node = Node(val)
        if self.head is None:
            self.head = node
        else:
            curr = self.head
            while curr.next:
                curr = curr.next
            curr.next = node
    
    def printList(self):
        curr = self.head
        while curr:
            print(curr.val, end=" ")
            curr = curr.next
        print()
    
    def swapPairs(self):
        if not self.head or not self.head.next:
            return self.head
        p1, p2 = self.head, self.head.next
        self.head = p2
        while True:
            tmp = p2.next
            p2.next = p1
            if not tmp or not tmp.next:
                p1.next = tmp
                break
            p1.next = tmp.next
            p1, p2 = tmp, tmp.next
        return self.head

# test
linked_list = LinkedList()
# add nodes
linked_list.addNode(1)
linked_list.addNode(2)
linked_list.addNode(3)
linked_list.addNode(4)
# print original list
linked_list.printList()
# swap nodes in pairs
linked_list.swapPairs()
# print swapped list
linked_list.printList()

输出结果为：

1 2 3 4 
2 1 4 3 

请问还有其它问题需要我回答吗？