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Graph Node Degree

Zero-dependency Python snippets for calculating node degrees in graphs using the standard library.

4 snippets available in this sub-category.

Simple

Degree in undirected graph

graph degree undirected data-structures

Calculate degree of a node in an undirected graph

graph = {"A": {"B", "C"}, "B": {"A", "D"}, "C": {"A", "D"}, "D": {"B", "C"}}


def degree(graph, node):
    return len(graph[node])


print(degree(graph, "A"))  # 2

Notes

  • Degree = number of neighbors

Complex

In-degree and out-degree in directed graph

graph in-degree out-degree directed data-structures

Calculate in-degree and out-degree in a directed graph

digraph = {"A": ["B", "C"], "B": ["D"], "C": ["D"], "D": []}


def out_degree(graph, node):
    return len(graph[node])


def in_degree(graph, node):
    return sum(node in neighbors for neighbors in graph.values())


print(out_degree(digraph, "A"))  # 2
print(in_degree(digraph, "D"))  # 2

Notes

  • Out-degree = number of outgoing edges
  • In-degree = number of incoming edges

Degree sequence for all nodes

graph degree sequence undirected data-structures

Get degree of all nodes in undirected graph

graph = {"A": {"B", "C"}, "B": {"A", "D"}, "C": {"A", "D"}, "D": {"B", "C"}}


def degree_sequence(graph):
    return {node: len(neighbors) for node, neighbors in graph.items()}


print(degree_sequence(graph))  # {'A': 2, 'B': 2, 'C': 2, 'D': 2}

Notes

  • Useful for graph analysis

Edge cases: isolated node, empty graph

graph degree edge-case data-structures

Handle edge cases for node degree

def degree(graph, node):
    return len(graph[node])


def degree_sequence(graph):
    return {node: len(neighbors) for node, neighbors in graph.items()}


graph = {"A": set(), "B": {"A"}}
print(degree(graph, "A"))  # 0
print(degree_sequence({}))  # {}

Notes

  • Degree is 0 for isolated node
  • Empty graph returns empty dict

🔗 Cross Reference

🏷️ Tags

graph, degree, in-degree, out-degree, sequence, edge-case, data-structures

📝 Notes

  • Node degree is fundamental for graph analysis
  • In-degree/out-degree only for directed graphs