A memo when creating a directed graph using Graphviz in Python

A memo when creating a directed graph using Graphviz in Python

Operating environment

• Windows10 (64bit)
• Python 3.8.1
• Graphviz 2.38

Environment

First, install Graphviz on Windows.

https://graphviz.gitlab.io/_pages/Download/Download_windows.html

This time, I downloaded the msi. After downloading, execute it and install it according to the wizard. After installation, pass it through the path.

Next, install graphviz with pip.

pip install graphviz

Actually try

First of all, the simple one.

Code example

from graphviz import Digraph

graph = Digraph(format="png")

#Add node
graph.node("node1")
graph.node("node2")
graph.node("node3")
graph.node("node4")

#Add edge
graph.edge("node1", "node2")
graph.edge("node1", "node3")
graph.edge("node2", "node4")
graph.edge("node3", "node4")

#Save image
#No extension needed
graph.render("image/output")

#Display image
graph.view()

output

Code description

from graphviz import Digraph

graph = Digraph(format="png")

Import Digraph to create a directed graph. In addition to png, pdf and svg can also be output.

#Add node
graph.node("node1")
graph.node("node2")
graph.node("node3")
graph.node("node4")

Create a node. The given argument is drawn inside the node.

#Add edge
graph.edge("node1", "node2")
graph.edge("node1", "node3")
graph.edge("node2", "node4")
graph.edge("node3", "node4")

Create an edge. An arrow is attached in the direction of the first argument → the second argument.

As shown below, a new node will be created if you specify it here even if you have not created a node.

#Add edge
graph.edge("node1", "node2")
graph.edge("node1", "node3")
graph.edge("node2", "node4")
graph.edge("node3", "node4")
#Specify a node that has not been created
graph.edge("A", "B")

The output is as follows.

Change the appearance of the graph

You can change the shape and color of the node.

Shape change

Code example

from graphviz import Digraph

graph = Digraph(format="png")

#Add node
graph.attr("node", shape="square") #Make the shape square
graph.node("node1")
graph.node("node2")

graph.attr("node", shape="star") #Make the shape a star
graph.node("node3")
graph.node("node4")

graph.node("node5", shape="circle") #Can be set individually
graph.node("node6")

#Add edge
graph.edge("node1", "node2")
graph.edge("node1", "node3")
graph.edge("node2", "node4")
graph.edge("node3", "node4")
graph.edge("node4", "node5")
graph.edge("node4", "node6")

#Save image
#No extension needed
graph.render("image/output2")

#Display image
graph.view()

output

Code description

#Add node
graph.attr("node", shape="square") #Make the shape square
graph.node("node1")
graph.node("node2")

graph.attr("node", shape="star") #Make the shape a star
graph.node("node3")
graph.node("node4")

graph.node("node5", shape="circle") #Can be set individually
graph.node("node6")

You can change the settings of all nodes using the attr method.

You can specify the shape by setting shape =" (shape) ".

If you specify the shape when creating a node, you can change only the settings of that node.

Color change

Code example

from graphviz import Digraph

graph = Digraph(format="png")

#Appearance settings
graph.attr("node", style="filled", fillcolor="black", color="red") #Node color settings
graph.attr("edge", color="cyan") #Edge color setting

#Add node
graph.node("node1", style="filled", fillcolor="palegreen", fontcolor="blue")
graph.node("node2", style="filled", fillcolor="yellow")
graph.node("node3", fontcolor="magenta")
graph.node("node4", style="filled", fillcolor="#808080")
graph.node("node5", fontcolor="white")


#Add edge
graph.edge("node1", "node2")
graph.edge("node1", "node3")
graph.edge("node2", "node4")
graph.edge("node3", "node4")
graph.edge("node3", "node5")

#Save image
#No extension needed
graph.render("image/output3")

#Display image
graph.view()

output

Code description

#Appearance settings
graph.attr("node", style="filled", fillcolor="black", color="red") #Node color settings
graph.attr("edge", color="cyan") #Edge color setting

#Add node
graph.node("node1", style="filled", fillcolor="palegreen", fontcolor="blue")
graph.node("node2", style="filled", fillcolor="yellow")
graph.node("node3", fontcolor="magenta")
graph.node("node4", style="filled", fillcolor="#808080")
graph.node("node5", fontcolor="white")

The whole setting can be done by using the attr method, like when changing the shape. Nodes and edges can be set by setting the first argument to " node " or " edge ".

To fill it, use style =" filled " and fill color =" (color) ". To change the text color, use font color =" (color) ". The color can also be specified by the color code.

It can also be set individually when creating a node.

reference

Draw a beautiful graph using Graphviz on Python