How to keep nodes on the same rank using Python and Graphviz?

Question

So apparently the way to keep certain nodes in GraphViz on the same level is to use something like:

{rank = same; n5; n6; n7; n8;}

However, I'm trying to automate all of this inside Python using: https://graphviz.readthedocs.io/en/stable/index.html

And while I can figure out how to add basic attributed to the graph (such as a label), I cannot figure out how to specify that certain nodes need to be in the same rank from inside Python! I know that this can be done, but I cannot figure out the syntax. If you see here: http://graphviz.readthedocs.io/en/stable/manual.html#attributes

It even says that you can use "rank=same." So I know that it can be done, but I just cannot figure out how to do it.

Can somebody please provide a working example in Python where they specify that certain nodes are on the same rank (where they normally wouldn't be if the specification hadn't been made)? Thank you very much

Answer 1

您可以创建一个子图，其中包含您想要在同一等级上的节点，并将rank='same'设置为子图的属性。这是一个有三个节点的例子：

from graphviz import Graph

g = Graph('parent')

c = Graph('child')
c.attr(rank='same')
c.node('A')
c.node('B')
c.node('C')
c.edge('A', 'B') #without rank='same', B will be below A

g.subgraph(c)

print(g.source)

这会产生点源

graph parent {
    subgraph child {
        rank=same
        A
        B
        C
        A -- B
    }
}

并由dot呈现为

您还可以包含已在主图中定义的已定义的节点，这样您就可以创建所有节点，并定义其属性和边，然后为相同等级的每个节点组创建一个子图

例如，您将获得与以下相同的图表：

g = Graph('parent')

g.node('A')
g.node('B')
g.node('C')
g.edge('A', 'B') #without rank='same', B will be below A

c = Graph('child')
c.attr(rank='same')
c.node('A')
c.node('B')
c.node('C')

g.subgraph(c)