Example Bellman Ford algorithm in Python

bellman_ford.py

# this program initializes a graph with a given number of vertices, 
# adds edges to it, and then executes the bellman-ford algorithm to 
# find the shortest paths from a specified source vertex to all 
# other vertices in the graph. it also checks for negative weight 
# cycles in the graph.

class Graph:
    def __init__(self, vertices):
        self.V = vertices
        self.graph = []

    def add_edge(self, u, v, w):
        self.graph.append([u, v, w])

    def print_solution(self, dist):
        print("vertex distance from source")
        for i in range(self.V):
            print("{0}\t\t{1}".format(i, dist[i]))

    def bellman_ford(self, src):
        dist = [float("Inf")] * self.V
        dist[src] = 0

        for _ in range(self.V - 1):
            for u, v, w in self.graph:
                if dist[u] != float("Inf") and dist[u] + w < dist[v]:
                    dist[v] = dist[u] + w

        for u, v, w in self.graph:
            if dist[u] != float("Inf") and dist[u] + w < dist[v]:
                print("graph contains negative weight cycle")
                return

        self.print_solution(dist)


if __name__ == "__main__":
    g = Graph(5)
    g.add_edge(0, 1, -1)
    g.add_edge(0, 2, 4)
    g.add_edge(1, 2, 3)
    g.add_edge(1, 3, 2)
    g.add_edge(1, 4, 2)
    g.add_edge(3, 2, 5)
    g.add_edge(3, 1, 1)
    g.add_edge(4, 3, -3)

    g.bellman_ford(0)

# vertex distance from source
# 0               0
# 1               -1
# 2               2
# 3               -2
# 4               1