Algorithms For Dummies

 

»

NetworkX (

https://networkx.github.io/

): Contains code for draw-

ing graphs.

 

»

matplotlib (

http://matplotlib.org/

): Provides access to all sorts of 

drawing routines, some of which can display graphs created by NetworkX.

To use packages in Python, you must import them. When you need to use external 

packages, you must add special code, such as the following lines of code that pro-

vide access to 

matplotlib

 and 

networkx

. (You can find this code in the 

A4D; 08; 

Draw Graph.ipynb

 file on the Dummies site as part of the downloadable code; see 

the Introduction for details.)

import networkx as nx

import matplotlib.pyplot as plt

%matplotlib inline

The special 

%matplotlib inline

 entry lets you see your plots directly in the 

Notebook rather than as an external graphic. Using this entry means that you can 

create a Notebook with graphics already included so that you don’t have to run the 

code again to see the results you received in the past.

Now that you have access to the packages, you create a graph. In this case, a graph 

is a sort of container that holds the key attributes that define the graph. Creating 

a container lets you draw the graph so that you can see it later. The following code 

creates a NetworkX 

Graph

 object.

AGraph = nx.Graph()

Adding the key attributes to 

AGraph

 comes next. You must add both nodes and 

edges using the following code.

Nodes = range(1,5)

Edges = [(1,2), (2,3), (3,4), (4,5), (1,3), (1,5)]

As previously mentioned, 

Edges

 describe connections between 

Nodes

. In this case, 

Nodes

 contains values from 1 through 5, so 

Edges

 contains connections between 

those values.

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CHAPTER 8