我正在制作自己的merge_list函数。我已经制作了类SList（）和类_Node（）。但是，当我在merge_list中输入两个排序的列表时，merge_list函数无法比较两个节点的值，并显示type object '_Node' has no attribute '_element'，但是_Node类具有_element属性（我也尝试了element，但也不起作用）。我的功能出了什么问题？
这是我的class SList()和class _Node()的部分代码以及merge_list的完整代码
class SList:
class _Node:
def __init__(self, element, next=None):
self._element = element
self._next = next
def element(self):
return self._element
def next(self):
return self._next
def set_element(self, element):
self._element = element
def set_next(self, next):
self._next = next
def __init__(self, head=None):
self._head = head
def insert_first(self, element):
self._head = self._Node(element, self._head)
def insert_after(self, element, p):
new_node = self._Node(element, p.next())
p._next = new_node
。 。 。 和我的merge_list函数
def merge_list(s1, s2):
s3 = SList()
s3._Node(None, None)
prev = s3
while s1 != None and s2 != None:
if s1._Node._element<= s2._Node._element: # this line is the problem
prev.next = s1
s1 = s1.next
else:
prev.next = s2
s2 = s2.next
prev = prev.next
if s1 == None:
prev.next = s2
elif s2 == None:
prev.next = s1
return s3.next
完成此功能后，我输入了两个这样的排序列表，然后调用merge_list函数
if __name__ == "__main__":
s1 = SList()
s1.insert_first(1)
s1.insert_first(3)
s1.insert_first(5)
s1.insert_first(7)
s1.insert_first(9)
s1.insert_first(11)
s1.insert_first(13)
print(f"s1 :", s1)
s2 = SList()
s2.insert_first(2)
s2.insert_first(4)
s2.insert_first(6)
print(f"s2 : ", s2)
merge_list(s1, s2)
，输出为
Traceback (most recent call last):
s1 : 13 -> 11 -> 9 -> 7 -> 5 -> 3 -> 1 -> None: 7 element(s)
s2 : 6 -> 4 -> 2 -> None: 3 element(s)
File "", line 334, in <module>
merge_list(s1, s2)
File "", line 151, in merge_list
if s1._Node._element<= s2._Node._element:
AttributeError: type object '_Node' has no attribute '_element'
似乎s1，s2列表已成功创建，但无法比较该节点的值。 merge_list函数有什么问题？
答案 0 :(得分：0)
让我们一步一步地
class SList:
class _Node:
注释为什么在SList类中定义Node类？除非您从不希望从Slist外部访问Node（即使如此），否则这不是通常的做法
def __init__(self, element, next=None):
self._element = element
self._next = next
def element(self):
return self._element
def next(self):
return self._next
def set_element(self, element):
self._element = element
def set_next(self, next):
self._next = next
注释：初始化/获取器和设置器。到目前为止，一切都有意义。但是，我个人更喜欢@attrs库。但是我们稍后再讲。
def __init__(self, head=None):
self._head = head
def insert_first(self, element):
self._head = self._Node(element, self._head)
def insert_after(self, element, p):
new_node = self._Node(element, p.next())
p._next = new_node
def merge_list(s1, s2):
s3 = SList()
s3._Node(None, None)
prev = s3
while s1 != None and s2 != None:
if s1._Node._element<= s2._Node._element: # this line is the problem
由于注释中提到的原因，这根本行不通：_Node类没有_element属性。实例确实可以。
prev.next = s1
prev是s3，SList因此不应该在下一个属性吗？
s1 = s1.next
else:
prev.next = s2
s2 = s2.next
prev = prev.next
if s1 == None:
prev.next = s2
elif s2 == None:
prev.next = s1
return s3.next
class _Node:
def __init__(self, element, next=None):
self._element = element
self._next = next
@property
def element(self):
return self._element
@property
def next(self):
return self._next
def set_element(self, element):
self._element = element
def set_next(self, next):
self._next = next
class SList:
def __init__(self, head=None):
self._head = _Node(head)
@property
def head(self):
return self._head
def insert_first(self, element):
self._head = _Node(element, self._head)
def insert_after(self, element, p):
new_node = _Node(element, p.next())
p._next = new_node
def merge_list(s1, s2):
s3 = SList()
prev = s3._head
head_s1 = s1._head
head_s2 = s2._head
while (head_s1._element != None) and (head_s2._element != None):
if head_s1._element<= head_s2._element: # this line is the problem
prev.set_next(head_s1)
head_s1 = head_s1.next
else:
prev.set_next(head_s2)
head_s2 = head_s2.next
prev = prev.next
if head_s1 == None:
prev.set_next(head_s1)
elif head_s2 == None:
prev.set_next(head_s2)
return s3