在树形结构数据的类中，我尝试获取从某个节点到根的路径。get_forward_path()下面的方法在第一次运行中有效，但每次运行该方法时，其输出列表都会不断增长。即使我将该方法应用于不同的节点，它也会不断增长。为什么即使在调用该方法path时将参数重置为默认值（空白列表）也会发生这种情况？
class TreeNode:
def __init__(self, data):
self.data = data
self.children = []
self.parent = None
def add_child(self, child):
child.parent = self
self.children.append(child)
def print_tree(self):
spaces = ' ' * self.get_level() * 3
prefix = spaces + "|__" if self.parent else ""
print(prefix + self.data)
if self.children:
for child in self.children:
child.print_tree()
def get_forward_path(self,path=[]):
if not self.parent:
path.append(self.data)
else:
path.append(self.data)
p = self.parent
p.get_forward_path(path)
return path[::-1]
def get_level(self):
level = 0
p = self.parent
while p:
level += 1
p = p.parent
return level
root = TreeNode("Electronics")
laptop = TreeNode("Laptop")
Mac = TreeNode("Mac")
Surface = TreeNode("Surface")
ThinkPad = TreeNode("ThinkPad")
laptop.add_child(Mac)
laptop.add_child(Surface)
laptop.add_child(ThinkPad)
cellphone = TreeNode("Cell Phone")
iPhone = TreeNode("iPhone")
Google_Pixel = TreeNode("Google Pixel")
Vivo = TreeNode("Vivo")
cellphone.add_child(iPhone)
cellphone.add_child(Google_Pixel)
cellphone.add_child(Vivo)
tv = TreeNode("TV")
Samsung = TreeNode("Samsung")
LG = TreeNode("LG")
tv.add_child(Samsung)
tv.add_child(LG)
root.add_child(laptop)
root.add_child(cellphone)
root.add_child(tv)
root.print_tree()
Electronics
|__Laptop
|__Mac
|__Surface
|__ThinkPad
|__Cell Phone
|__iPhone
|__Google Pixel
|__Vivo
|__TV
|__Samsung
|__LG
Samsung.get_forward_path()
['Electronics', 'TV', 'Samsung']
Samsung.get_forward_path()
['Electronics', 'TV', 'Samsung', 'Electronics', 'TV', 'Samsung']
iPhone.get_forward_path()
['Electronics',
'Cell Phone',
'iPhone',
'Electronics',
'TV',
'Samsung',
'Electronics',
'TV',
'Samsung']