Python Coding challenge - Day 799| What is the output of the following Python Code?

 Code Explanation:

Import the NetworkX Library

import networkx as nx

Explanation:

networkx is a Python library for creating and analyzing graphs (networks).

It lets you work with nodes (points) and edges (connections) easily.

The alias nx is just a shorthand name to make the code shorter and cleaner.

Think of NetworkX as a tool for representing relationships — like cities connected by roads, or people connected in a social network.

Create an Empty Graph Object

G = nx.Graph()

Explanation:

nx.Graph() creates an empty, undirected graph object and stores it in the variable G.

Undirected means the connection (edge) has no direction —

for example, an edge between nodes 1 and 2 means 1 is connected to 2 and 2 is connected to 1.

At this point:

Number of nodes = 0

Number of edges = 0

Add Multiple Edges to the Graph

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

Explanation:

.add_edges_from() adds several edges at once to the graph G.

Each tuple (a, b) represents an edge between node a and node b.

What happens step by step:

Edge (1, 2) → connects node 1 and node 2

Edge (2, 3) → connects node 2 and node 3

Edge (3, 4) → connects node 3 and node 4

NetworkX automatically adds nodes when they appear in an edge.

You don’t have to add nodes manually.

Now the graph contains:

Nodes: 1, 2, 3, 4

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

Visual structure:

1 —— 2 —— 3 —— 4

Count and Print the Number of Nodes

print(G.number_of_nodes())

Explanation:

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

After the previous step, the graph has four unique nodes: 1, 2, 3, and 4.

Output:

4

500 Days Python Coding Challenges with Explanation