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Finding nodes involved in triangles

NetworkX provides an API for counting the number of triangles that every node is involved in: nx.triangles(G). It returns a dictionary of nodes as the keys and number of triangles as the values. Your job in this exercise is to modify the function defined earlier to extract all of the nodes involved in a triangle relationship with a given node.

This exercise is part of the course

Introduction to Network Analysis in Python

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Exercise instructions

  • Write a function nodes_in_triangle() that has two parameters - G and n - and identifies all nodes in a triangle relationship with a given node.
    • In the for loop, iterate over all possible triangle relationship combinations.
    • Check whether the nodes n1 and n2 have an edge between them. If they do, add both nodes to the set triangle_nodes.
  • Use your function in an assert statement to check that the number of nodes involved in a triangle relationship with node 1 of graph T is equal to 35.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

from itertools import combinations

# Write a function that identifies all nodes in a triangle relationship with a given node.
def nodes_in_triangle(G, n):
    """
    Returns the nodes in a graph `G` that are involved in a triangle relationship with the node `n`.
    """
    triangle_nodes = set([n])

    # Iterate over all possible triangle relationship combinations
    for n1, n2 in ____:

        # Check if n1 and n2 have an edge between them
        if ____:

            # Add n1 to triangle_nodes
            ____

            # Add n2 to triangle_nodes
            ____

    return triangle_nodes

# Write the assertion statement
assert len(____(____, ____)) == ____
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