graph_list.py

#!/usr/bin/python
# encoding=utf8

from __future__ import print_function
# Author: OMKAR PATHAK

# We can use Python's dictionary for constructing the graph.

class AdjacencyList(object):
    def __init__(self):
        self.List = {}

    def addEdge(self, fromVertex, toVertex):
        # check if vertex is already present
        if fromVertex in self.List.keys():
            self.List[fromVertex].append(toVertex)
        else:
            self.List[fromVertex] = [toVertex]

    def printList(self):
        for i  in self.List:
            print((i,'->',' -> '.join([str(j) for j in self.List[i]])))

if __name__ == '__main__':
    al = AdjacencyList()
    al.addEdge(0, 1)
    al.addEdge(0, 4)
    al.addEdge(4, 1)
    al.addEdge(4, 3)
    al.addEdge(1, 0)
    al.addEdge(1, 4)
    al.addEdge(1, 3)
    al.addEdge(1, 2)
    al.addEdge(2, 3)
    al.addEdge(3, 4)

    al.printList()

    # OUTPUT:
    # 0 -> 1 -> 4
    # 1 -> 0 -> 4 -> 3 -> 2
    # 2 -> 3
    # 3 -> 4
    # 4 -> 1 -> 3