Python合并两个链表

感受python语言的优美的写法：

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

class Solution(object):
	def combine(self,list2, list3):

		if list2==None:
			return list3

		if list3==None:
			return list2

		dummy  = ListNode(-1)
		temp = dummy

		while list2!=None and list3!=None:
			if list2.val<=list3.val:
				temp.next = list2
				list2 = list2.next
				temp = temp.next
			else:
				temp.next = list3
				list3 = list3.next
				temp = temp.next

		if list2!=None:
			temp.next = list2

		if list3!=None:
			temp.next = list3

		return dummy.next


if __name__ == "__main__":

	node1 = ListNode(2)
	node2 = ListNode(3)
	node3 = ListNode(4)

	node1.next = node2
	node2.next = node3
	node3.next = None

	h2 = ListNode(3)
	h3 = ListNode(4)
	h4 = ListNode(8)

	h2.next = h3
	h3.next = h4
	h4.next = None

	s = Solution()
	res = s.combine(node1, h2)

	while res:
		print(res.val, end=" ")
		res = res.next