def swap_nodes(self, key_1, key_2):

        if key_1 == key_2:
            return 

        prev_1 = None 
        curr_1 = self.head 
        while curr_1 and curr_1.data != key_1:
            prev_1 = curr_1 
            curr_1 = curr_1.next

        prev_2 = None 
        curr_2 = self.head 
        while curr_2 and curr_2.data != key_2:
            prev_2 = curr_2 
            curr_2 = curr_2.next

        if not curr_1 or not curr_2:
            return 

        if prev_1:
            prev_1.next = curr_2
        else:
            self.head = curr_2

        if prev_2:
            prev_2.next = curr_1
        else:
            self.head = curr_1
            
        print('Before Swap')
        print('current 1 next:', curr_1.data)
        print('current 2 next:', curr_2.data)
        
        curr_1.next, curr_2.next = curr_2.next, curr_1.next
        
        print('\nAfter Swap')
        print('current 1 next:', curr_1.data)
        print('current 2 next:', curr_2.data)
        
    ''' Alternate swap node function , swap by changing the data attribute of node '''
    def swap_nodes_alt(self, key_1, key_2):
        if key_1 == key_2:
            return
        curr  = self.head
        x , y = None , None # Assign None to avoid reference error
        while curr :
            if curr.data == key_1:
                x = curr # key_1 found
            if curr.data == key_2:
                y =curr # key_2 found
            curr = curr.next
        
        if x and y: # Check if both key's exist
            x.data , y.data = y.data , x.data
        else : 
            return