# mininet.topo.MultiGraph

表示一个图结构。 类似于networkx中的图G(V,E)的概念。主要维护节点、边信息。 在MultiGraph中，节点就是一个序号，边则通过节点和节点所对应的连接列表中元素来表示。节点和节点的连接列表的对应关系通过字典结构来维护。

## **init**

```
def __init__( self ):
        self.data = {}
```

图结构最主要的功能就是维护一个字典。Key 是节点，value 是该节点所连接的所有的其他节点的列表。

```
add_node
    def add_node( self, node ):
        "Add node to graph"
        self.data.setdefault( node, [] )
```

添加一个节点，实际上就是添加一个 key 到 data 字典中。

```
add_edge
    def add_edge( self, src, dest ):
        "Add edge to graph"
        src, dest = sorted( ( src, dest ) )
        self.add_node( src )
        self.add_node( dest )
        self.data[ src ].append( dest )
```

添加一条边，实际上就是添加两个节点，然后将连接信息放到 data 字典中（需要注意的是一条边的信息仅被保存了一次，即放到序号较小的节点对应的 list 中）。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://yeasy.gitbook.io/mininet_book/module_topo/multigraph.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.