Cycle Detection

This example demonstrates the use of nx.find_cycle to find a single, arbitrary cycle in a graph.

Other functions like nx.simple_cycles and nx.cycle_basis can be used to find all cycles or a cycle basis.

[(2, 3, 'forward'), (3, 4, 'forward'), (4, 2, 'forward')]

import networkx as nx
import matplotlib.pyplot as plt

# Create a simple directed graph with a cycle
G = nx.DiGraph([(1, 2), (2, 3), (3, 4), (4, 2), (3, 5), (3, 2), (1, 5)])

# Draw the graph
pos = nx.spring_layout(G, seed=8020)
nx.draw(G, pos, with_labels=True)

# The `orientation` parameter can be used to determine how directed edges are
# treated and the reporting of edge direction in the cycle
cycle = nx.find_cycle(G, orientation="original")
print(cycle)

# Highlight the cycle in red
nx.draw_networkx_edges(G, pos, edgelist=cycle, edge_color="r", width=2)
plt.show()