DFS in python

# Python3 program to print DFS traversal
# from a given given graph
from collections import defaultdict

# This class represents a directed graph using
# adjacency list representation
class Graph:

# Constructor
def __init__(self):

# default dictionary to store graph
self.graph = defaultdict(list)

# function to add an edge to graph
def addEdge(self, u, v):
self.graph[u].append(v)

# A function used by DFS
def DFSUtil(self, v, visited):

# Mark the current node as visited
# and print it
visited[v] = True
print(v, end = ' ')

# Recur for all the vertices
# adjacent to this vertex
for i in self.graph[v]:
if visited[i] == False:
self.DFSUtil(i, visited)

# The function to do DFS traversal. It uses
# recursive DFSUtil()
def DFS(self, v):

# Mark all the vertices as not visited
visited = [False] * (len(self.graph))

# Call the recursive helper function
# to print DFS traversal
self.DFSUtil(v, visited)

# Driver code

# Create a graph given
# in the above diagram
g = Graph()
g.addEdge(0, 1)
g.addEdge(0, 2)
g.addEdge(1, 2)
g.addEdge(2, 0)
g.addEdge(2, 3)
g.addEdge(3, 3)

print("Following is DFS from (starting from vertex 2)")
g.DFS(2)