Stack using double linked list

data_structures/stacks/stack_using_dll.py

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+# A complete working Python program to demonstrate all  
+# stack operations using a doubly linked list  
+
+# Node class  
+class Node: 
+
+# Function to initialise the node object 
+    def __init__(self, data): 
+        self.data = data # Assign data 
+        self.next = None # Initialize next as null 
+        self.prev = None # Initialize prev as null         
+
+# Stack class contains a Node object 
+class Stack: 
+    # Function to initialize head  
+    def __init__(self): 
+        self.head = None
+
+# Function to add an element data in the stack  
+    def push(self, data): 
+
+        if self.head is None: 
+            self.head = Node(data) 
+        else: 
+            new_node = Node(data) 
+            self.head.prev = new_node 
+            new_node.next = self.head 
+            new_node.prev = None
+            self.head = new_node 
+
+
+# Function to pop top element and return the element from the stack  
+    def pop(self): 
+
+        if self.head is None: 
+            return None
+        else: 
+            temp = self.head.data 
+            self.head = self.head.next
+            self.head.prev = None
+            return temp 
+
+
+# Function to return top element in the stack  
+    def top(self): 
+
+        return self.head.data 
+
+
+# Function to return the size of the stack  
+    def size(self): 
+
+        temp = self.head 
+        count = 0
+        while temp is not None: 
+            count = count + 1
+            temp = temp.next
+        return count 
+
+
+# Function to check if the stack is empty or not   
+    def isEmpty(self): 
+
+        if self.head is None: 
+           return True
+        else: 
+           return False
+
+
+# Function to print the stack 
+    def printstack(self): 
+
+        print("stack elements are:") 
+        temp = self.head 
+        while temp is not None: 
+            print(temp.data, end ="->") 
+            temp = temp.next           
+
+
+# Code execution starts here          
+if __name__=='__main__':  
+
+# Start with the empty stack 
+  stack = Stack() 
+
+# Insert 4 at the beginning. So stack becomes 4->None  
+  print("Stack operations using Doubly LinkedList") 
+  stack.push(4) 
+
+# Insert 5 at the beginning. So stack becomes 4->5->None  
+  stack.push(5) 
+
+# Insert 6 at the beginning. So stack becomes 4->5->6->None  
+  stack.push(6) 
+
+# Insert 7 at the beginning. So stack becomes 4->5->6->7->None  
+  stack.push(7) 
+
+# Print the stack 
+  stack.printstack() 
+
+# Print the top element 
+  print("\nTop element is ", stack.top()) 
+
+# Print the stack size 
+  print("Size of the stack is ", stack.size()) 
+
+# pop the top element 
+  stack.pop() 
+
+# pop the top element 
+  stack.pop() 
+
+# two elements are popped 
+# Print the stack 
+  stack.printstack() 
+
+# Print True if the stack is empty else False 
+  print("\nstack is empty:", stack.isEmpty())