类实例的自动递增ID

本文介绍了类实例的自动递增ID的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

免责声明:这是我目前正在研究的一个学期项目.我的问题是关于实现级别的细节，而不是评分方案的一部分.我只是在编写此代码，以此来检验我将为我将要写的论文提出的理论.

Disclaimer: This is for a semester project that I am currently working on. My question is regarding an implementation level detail and is not part of the grading scheme. I am only writing this code as a way to test the theory that I am proposing for the paper that I will write.

我还考虑了这个问题的答案运气不好，所以请不要将此视为该问题的重复

Also, I have considered the answers for this question with little luck, so please do not consider this as a duplicate of that question

问题:

我有一个图(G =(V，E)).在算法的某个时刻，我需要通过将多个节点(例如v_1, v_2, ..., v_n)折叠"到一个节点(例如v)来将其转变为超图(在某种意义上).在问题的上下文中，这意味着我需要更改E中的边，以使V中的任何v_1, v_2, v_n与任何其他节点u之间的任何边e都被更改，使得e现在在u和v之间.

I have a graph (G=(V,E)). At some point in my algorithm, I need to turn this into a hypergraph (in a sense) by "collapsing" multiple nodes (say, v_1, v_2, ..., v_n) into one node (say, v). In the context of the problem, this implies that I need to change the edges in E such that any edge e between any of v_1, v_2, v_n and any other node u in V will be changed such that e is now between u and v.

为了捕获现在在任意一对节点之间可能存在多个不同的边缘，我需要为每个边缘创建一个唯一的标识符.我已经尝试通过ID和ID来执行此操作，而我目前无法正确实现.

In order to capture that there may now exist multiple distinct edges between any pair of nodes, I need to make a unique identifier for each edge. I have tried to do this by means of and ID, which I am currently unable to properly implement.

这是我尝试过的:

class Edge: _ID = 0 def __init__(self, u, v, w, c,f=0): self.id = Edge._ID Edge._ID += 1 self.src = u self.dest = v self.weight = w self.capacity = c self.flow = f

但是，当我尝试实例化新边缘时，出现以下错误:

However, when I try to instantiate a new edge, I get the following error:

>>> e = Edge(1,3,5,10,0) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "UnsplittableFlow.py", line 14, in __init__ self.id = Edge._ID; Edge._ID += 1 UnboundLocalError: local variable '_ID' referenced before assignment

编辑:

有了一些答案的建议，我已经能够解决实例化时间错误.但是，另一个错误仍然存​​在.这是我的代码和错误:

With the suggestions of some answers, I have been able to fix the instantiation-time error. However, another error persists. Here is my code and the errors:

class Edge: _ID = 0 def __init__(self, u, v, w, c,f=0): self.id = self._ID; self._ID += 1 self.src = u self.dest = v self.weight = w self.capacity = c self.flow = f

错误:

>>> e = Edge(1,3,5,10,0) >>> e.id 0 >>> Edge._ID 0 >>> f = Edge(2,3,5,10,0) >>> f.id 0 >>> Edge._ID 0

我将不胜感激

谢谢

推荐答案

您仍然可以使用self到达_ID.

self.id = self._ID self.__class__._ID += 1

如果您使用的是CPython，则可以拥有一个懒人的ID:

If you're using CPython, you can have a lazy man's ID:

class Edge(object): @property def id(self): return id(self)