What is NetworkX?

A Python library used to create, manipulate, and study graphs and networks (social, transportation, web, etc.)

📖 Key Definitions

• Graph: A structure made up of nodes (vertices) and edges (links).
• Node: A data point (e.g., a city, person, website).
• Edge: A connection between two nodes.
• Directed Graph: Connections that flow in one direction (A → B).
• Undirected Graph: Connections that flow both ways (A ↔ B).
• Weighted Graph: Edges with numeric values (weights).
• Multigraph: A graph allowing multiple edges between the same nodes.

Create and Inspect a Graph

📌 Code: Create an Undirected Graph

import networkx as nx 

# Create an undirected graph
G = nx.Graph()

# Add a single node labeled "A" to the graph
G.add_node("A")

# Add multiple nodes: "B" and "C" to the graph
G.add_nodes_from(["B", "C"])

# Add an edge (connection) between nodes "A" and "B"
G.add_edge("A", "B")

# Add multiple edges to the graph: one between "B" and "C", another between "C" and "A"
G.add_edges_from([("B", "C"), ("C", "A")])

# Print all nodes in the graph
print("Nodes:", G.nodes)

# Print all edges in the graph
print("Edges:", G.edges)

🧠 Exam Concept: Undirected vs Directed Graph

• Undirected: A symmetrical relationship (e.g., friendship between two people)
• Directed: A one-way relationship (e.g., one person following another)

➰ Directed Graph Example