use a singly linked list create a stack python

1'''Python supports automatic garbage collection so deallocation of memory 
2is done implicitly. However to force it to deallocate each node after use, 
3add the following code: 
4  
5    import gc         #added at the start of program 
6    gc.collect()     #to be added wherever memory is to be deallocated 
7'''
8  
9class Node: 
10      
11    # Class to create nodes of linked list 
12    # constructor initializes node automatically 
13    def __init__(self,data): 
14        self.data = data 
15        self.next = None
16      
17class Stack: 
18      
19    # head is default NULL 
20    def __init__(self): 
21        self.head = None
22      
23    # Checks if stack is empty 
24    def isempty(self): 
25        if self.head == None: 
26            return True
27        else: 
28            return False
29      
30    # Method to add data to the stack 
31    # adds to the start of the stack 
32    def push(self,data): 
33          
34        if self.head == None: 
35            self.head=Node(data) 
36              
37        else: 
38            newnode = Node(data) 
39            newnode.next = self.head 
40            self.head = newnode 
41      
42    # Remove element that is the current head (start of the stack) 
43    def pop(self): 
44          
45        if self.isempty(): 
46            return None
47              
48        else: 
49            # Removes the head node and makes  
50            #the preceeding one the new head 
51            poppednode = self.head 
52            self.head = self.head.next
53            poppednode.next = None
54            return poppednode.data 
55      
56    # Returns the head node data 
57    def peek(self): 
58          
59        if self.isempty(): 
60            return None
61              
62        else: 
63            return self.head.data 
64      
65    # Prints out the stack      
66    def display(self): 
67          
68        iternode = self.head 
69        if self.isempty(): 
70            print("Stack Underflow") 
71          
72        else: 
73              
74            while(iternode != None): 
75                  
76                print(iternode.data,"->",end = " ") 
77                iternode = iternode.next
78            return
79          
80# Driver code 
81MyStack = Stack() 
82  
83MyStack.push(11)  
84MyStack.push(22) 
85MyStack.push(33) 
86MyStack.push(44) 
87  
88# Display stack elements  
89MyStack.display() 
90  
91# Print top element of stack  
92print("\nTop element is ",MyStack.peek()) 
93  
94# Delete top elements of stack  
95MyStack.pop() 
96MyStack.pop() 
97  
98# Display stack elements 
99MyStack.display() 
100  
101# Print top element of stack  
102print("\nTop element is ", MyStack.peek())  
103  
104# This code is contributed by Mathew George