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我有两个类BaseNodeBaseEdge我可以使用connect方法通过这些类中的边缘连接两个节点。

代码

这是我的BaseNode

class BaseNode:
  def __init__(self,edges=[],value=None,edges_limit=math.inf):
    self.edges = edges
    self.value = value
    self.limit = edges_limit
    self.edge_class = BaseEdge
    self.adjs = []

  def get_adjacents(self):
    if not self.edges:
        return []
    for edge in self.edges :
        self.adjs.append(edge.n2)
    return self.adjs

  def get_edges(self):
    return self.edges

  def connect(self,other):
    """
    connect two nodes by connecting an edge between them
    """
    if not isinstance(other,self.__class__):
        raise ValueError(f'Node should be type of {self.__class__.__name__}')
    if len(self.edges) == self.limit :
        raise MaximumEdgeReached(f'maximum edge reached the limit is {self.limit} ')
    e = BaseEdge()
    e.set_nodes(self,other)
    self.edges.append(e)

BaseEdge类:

class BaseEdge:
  def __init__(self):
    self.n1 = None
    self.n2 = None
    self.node_class = BaseNode

  def get_nodes(self):
    return (self.n1,self.n2,)

  def set_nodes(self,n1,n2):
    a = isinstance(n1,self.node_class)
    b = isinstance(n2,self.node_class)

    if not a and b :
        raise ValueError(f'nodes of this edge should be {self.node_class}')
    self.n1 = n1
    self.n2 = n2

  def connect(self,n1=None,n2=None):
    if not self.n1 and self.n2 :
        self.set_nodes(n1,n2)
    self.n1.edges.append(self)
    self.n2.edges.append(self)

我试过什么?

我试图连接两者的点头BaseNodeBaseEdge查看结果。节点应该具有相同的边缘,但发生了 2 个问题:

  1. edges的属性,n1它们n2是第一个节点和第二个节点,有 2 个实例,e其中是边!但edges应该有 1 个实例BaseEdge
  2. 当我创建新对象时BaseNode,该edges属性对它们具有相同的值!.
    >>> n1 = BaseNode()
    >>> n2 = BaseNode()
    >>> e = BaseEdge()
    >>> e.set_nodes(n1,n2)
    >>> e.connect()
    >>> n2.edges
    [<__main__.BaseEdge object at 0x0000000003282BA8>, <__main__.BaseEdge object at 0x0000000003282BA8>]
    >>> n1.edges
    [<__main__.BaseEdge object at 0x0000000003282BA8>, <__main__.BaseEdge object at 0x0000000003282BA8>]
    >>> n3 = BaseNode() #initializing new oject
    >>> n3.edges
    [<__main__.BaseEdge object at 0x0000000003282BA8>, <__main__.BaseEdge object at 0x0000000003282BA8>]

注意:当我使用类connect的方法时BaseNode。它也有同样的问题。

BaseNode类就像一个单态类。它不应该是!请帮我解决这个问题。

4

1 回答 1

1

这是旧的可变默认参数问题——为避免再次全部输入,我建议您阅读以下内容:https ://florimond.dev/blog/articles/2018/08/python-mutable-defaults-are-the-万恶之源/

本质上,而不是像这样定义一个函数..

def my_function(input_list=[]):
   input_list.append(2)
   ...

您应该将其定义为

def my_function(input_list=None):
   if input_list is None:
      input_list = []

   input_list.append(2)
   ...

[]这可以防止在对函数的后续调用中重新使用默认参数。

于 2020-11-30T19:41:54.563 回答