Question

我正在使用LinkedLists上的Codewars Kata，并继续收到错误AttributeError：'NoneType'对象没有属性'data'

class Node(object):
    def __init__(self, data):
        self.data = data
        self.next = None`

def push(head, data):
    if data == None: return
    new_node = Node(data)
    new_node.next = head
    head = new_node

def build_one_two_three():
    head = None
    push(head, 3)
    push(head, 2)
    push(head, 1)
    return head

我认为使用if data == None可以解决问题，但事实并非如此。任何建议都将不胜感激。

Answer 1

push函数中的行head = new_node正在替换head指向的本地引用，而不是build_one_two_three函数中head引用的数据。尝试推送返回头，并更新build_one_two_three，其中每次推送更新引用：head = push(head,1)等。

Answer 2

我猜您正在寻找以下内容：

class Node(object):
    def __init__(self, data):
        self.data = data
        self.next = None

def push(head, data):
    if data == None: return
    new_node = Node(data)
    new_node.next = head
    head = new_node
    return head

def build_one_two_three():
    head = None
    head = push(head, 3)
    head = push(head, 2)
    head = push(head, 1)
    return head
# Just to pretty-print the linked list.
def pp(head):
    res = ""
    node = head
    while node != None:
        res += "%s -> " % node.data
        node = node.next
    res += "None"
    print res

if __name__ == "__main__":
   head = build_one_two_three()
   pp(head)

问题是每次推送新节点时都会覆盖head的引用。

LinkedList AttributeError：'NoneType'对象没有属性'data'

2 个答案: