17_graphsWithAdjMatrixHashmap.py

class Graph:
    def __init__(self, vertices: list[str], is_dir: bool):
        self.is_dir = is_dir
        self.adj = {v: set() for v in vertices}

    def _check(self, v):
        if v not in self.adj:
            raise KeyError(f"Vertex {v!r} not in graph")

    def add_vertex(self, v: str):
        if v not in self.adj:
            self.adj[v] = set()

    def connect_edge(self, u: str, v: str):
        self._check(u); self._check(v)
        self.adj[u].add(v)
        if not self.is_dir:
            self.adj[v].add(u)
        print(f"edge created: {u} -> {v}" + ("" if self.is_dir else " (undirected)"))

    def disconnect_edge(self, u: str, v: str):
        self._check(u); self._check(v)
        self.adj[u].discard(v)
        if not self.is_dir:
            self.adj[v].discard(u)
        print(f"edge removed: {u} -/-> {v}" + ("" if self.is_dir else " (undirected)"))

    def get_graph(self):
        for v in self.adj:
            print(f"{v}: {sorted(self.adj[v])}" if self.adj[v] else f"{v}: []")

g = Graph(["a","b","c","d"], is_dir=False)
g.get_graph()
g.connect_edge("a","b")
g.connect_edge("b","c")
g.connect_edge("c","d")
g.connect_edge("d","a")
g.connect_edge("a","c")
g.get_graph()
g.disconnect_edge("a","c")
g.get_graph()