Python Coding challenge - Day 798| What is the output of the following Python Code?

 

Code Explanation:

1) Import the NetworkX library

import networkx as nx

What this does:

Imports the networkx package and gives it the alias nx. NetworkX is a Python library for creating, manipulating, and analysing graphs and networks (nodes + edges).

2) Create an empty undirected graph

G = nx.Graph()

What this does:

Creates an empty undirected graph object G.

At this moment G has 0 nodes and 0 edges.

nx.Graph() means edges have no direction (edge (1,2) equals (2,1)).

(There are other graph types too, e.g. DiGraph for directed graphs.)

3) Add multiple edges to the graph

G.add_edges_from([(1, 2), (2, 3), (3, 4)])

What this does, step-by-step:

add_edges_from() takes a list of edge tuples. Each tuple (a, b) creates an edge between node a and node b.

NetworkX automatically adds the nodes referenced by the edges if those nodes do not already exist.

So after this line the graph contains:

Edges: (1,2), (2,3), (3,4)

Nodes: 1, 2, 3, 4 (added implicitly)

Conceptual picture:

1 — 2 — 3 — 4

4) Print the number of nodes

print(G.number_of_nodes())

What this does:

G.number_of_nodes() returns the total count of unique nodes in G.

Because edges added nodes 1,2,3,4, the function returns 4.

print(...) displays that value.

Output you get:

4

500 Days Python Coding Challenges with Explanation