Transform a neighbors table into GraphViz source code for visualization purposes.

graphviz-compiler.py

from graphviz import Digraph
from collections import deque

# There are three ways to model a graph:
# 1. Edge list: [(Vertex, Vertex)]
# 2. Neighbors table: Map(Vertex, [Vertex])
# 3. Adjacency matrix: [[Boolean]]
#
# The following graph is a neighbors table.
g = {
    'a': [('b', 3), ('c', 5)],
    'b': [('c', 4), ('d', 2)],
    'c': [('d', 2), ('e', 2), ('f', 1)],
    'd': [('c', 2), ('f', 1)],
    'e': [('g', 1), ('f', 2)],
    'f': [('g', 6), ('e', 2)],
    'g': [],
}


# to_graphviz :: Vertex -> Map(Vertex, [(Vertex, Weight)]) -> String
def to_graphviz(start, g):
    """Compiles the graph into GraphViz."""
    d = Digraph()
    q = deque()
    seen = set()

    q.append(start)

    while q:
        v = q.popleft()
        if v in seen:
            continue
        d.node(v, label=v)

        for x, w in g[v]:
            d.edge(v, x, label=str(w))
            q.append(x)
        seen.add(v)

    return d.source


with open('/tmp/test.gv', 'w') as f:
    src = to_graphviz('a', g)
    f.write(src)
    print('/tmp/test.gv created!')