# Topological sort | Python

## CodeCatch

### April 26th, 2021 04:27:00 PM

```					#Python program to print topological sorting of a DAG
from collections import defaultdict

#Class to represent a graph
class Graph:
def __init__(self,vertices):
self.graph = defaultdict(list) #dictionary containing adjacency List
self.V = vertices #No. of vertices

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

# A recursive function used by topologicalSort
def topologicalSortUtil(self,v,visited,stack):

# Mark the current node as visited.
visited[v] = True

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

# Push current vertex to stack which stores result
stack.insert(0,v)

# The function to do Topological Sort. It uses recursive
# topologicalSortUtil()
def topologicalSort(self):
# Mark all the vertices as not visited
visited = [False]*self.V
stack =[]

# Call the recursive helper function to store Topological
# Sort starting from all vertices one by one
for i in range(self.V):
if visited[i] == False:
self.topologicalSortUtil(i,visited,stack)

# Print contents of stack
print(stack)

g= Graph(6)