Added DFS code in python

Python implementation DataStructures/dfs.py

@@ -0,0 +1,53 @@
+import collections
+
+class Graph:
+    def __init__(self):
+        self.adjList = collections.defaultdict(set)
+
+    def addEdge(self, node1, node2):
+        self.adjList[node1].add(node2)
+        self.adjList[node2].add(node1)
+
+def dfsHelper(current, graph, visited, visitFunc):
+    if (visited[current]):
+        return
+
+    visited[current] = True;
+
+    visitFunc(current)
+
+    for neighbor in graph.adjList[current]:
+        dfsHelper(neighbor, graph, visited, visitFunc)
+
+
+def dfs(current, graph, visitFunc):
+    visited = collections.defaultdict(bool)
+    dfsHelper(current, graph, visited, visitFunc)
+
+def visitPrint(i):
+    print(i)
+
+# Testing the depth first search implementation
+if __name__ == "__main__":
+
+    # Testing on this tree
+    #      1
+    #     / \
+    #    /   \
+    #   2     3
+    #  / \   / \
+    # 4   5 6   7
+
+    g = Graph()
+    g.addEdge(1, 2)
+    g.addEdge(1, 3)
+    g.addEdge(2, 4)
+    g.addEdge(2, 5)
+    g.addEdge(3, 6)
+    g.addEdge(3, 7)
+
+    print("Test 1:")
+    dfs(1, g, visitPrint)
+
+    print("\nTest2:")
+    dfs(2, g, visitPrint)