depth-first search in Python

dfs.py

# Using a dictionary to act as an adjacency list
graph = {
    'A' : ['B','C'],
    'B' : ['D', 'E'],
    'C' : ['F'],
    'D' : [],
    'E' : ['F'],
    'F' : []
}

# visited: Set to keep track of visited nodes.

def dfs(visited, graph, node):
    if node not in visited:
        print (node)
        visited.add(node)
        for neighbour in graph[node]:
            dfs(visited, graph, neighbour)

def iterative_dfs(visited, graph, node):
    stack = [node]
    while stack:
        node = stack.pop()
        if node not in visited:
            print (node)
            visited.add(node)
            for neighbour in reversed(graph[node]):
                stack.append(neighbour)

# Driver Code
dfs(set(), graph, 'A')
iterative_dfs(set(), graph, 'A')