Doubly Final

class Node:
    def __init__(self, data):
        self.prev = None
        self.data = data
        self.next = None

class Doubly:
    def __init__(self):
        self.head = None

    def insert_begin(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
        else:
            new_node.next = self.head
            self.head.prev = new_node
            self.head = new_node

    def insert_end(self, data):
        new_node = Node(data)
        current = self.head
        if self.head is None:
            self.head = new_node
        else:
            while current.next != None:
                current = current.next
            current.next = new_node
            new_node.prev = current

    def insert_before(self, key, data):
        new_node = Node(data)
        current = self.head
        if self.head is None:
            print('List is empty')
            return
        if current.data == key:
            new_node.next = self.head
            self.head.prev = new_node
            return
        while current.data != key:
            current = current.next
        current.prev.next = new_node
        new_node.next = current
        current.prev = new_node

    def insert_after(self, key, data):
        new_node = Node(data)
        current = self.head
        if current.data == key:
            post_current = current.next
            current.next = new_node
            new_node.prev = current
            new_node.next = post_current
            post_current.prev = new_node
            return
        if self.head is None:
            print('Empty')
            return
        while current.data != key:
            current = current.next
            post_current = current.next
            if current.data != key and current.next is None:
                print('Empty')
                return
            if post_current.next is None and post_current.data == key:
                post_current.next = new_node
                new_node.prev = post_current
                return
        current.next = new_node
        new_node.prev = current
        new_node.next = post_current
        post_current.prev = new_node

    def del_first(self):
        current = self.head
        if self.head is None:
            print('Empty')
        else:
            self.head = current.next
            self.head.prev = None

    def del_last(self):
        current = self.head
        if self.head is None:
            print('empty')
        else:
            while current.next != None:
                pre_current = current
                current = current.next
            pre_current.next = None

    def del_given(self, key):
        current = self.head
        if self.head is None:
            print('empty')
            return
        if current.data == key:
            current = current.next
            current.prev = None
            self.head = current
            return
        while current.data != key:
            current = current.next
        current.prev.next = current.next


    def display(self):
        current = self.head
        while current != None:
            print(current.data, '', end='')
            current = current.next

    def concatenated(self, d1):
        current = self.head
        while current.next != None:
            current = current.next
        current.next = d1.head

d = Doubly()
d1 = Doubly()

#5 8 9 10
d.insert_begin(10)
d.insert_begin(9)
d.insert_begin(8)
d.insert_begin(5)
d.insert_end(11)
d.insert_end(20)
d.insert_before(8, 90)
d.insert_after(20, 100)
d.del_last()
# d.del_given(20)
print('xa')
d.display()
print()
d1.insert_begin(1)
d1.insert_begin(2)
d1.insert_begin(5)
d1.insert_begin(8)




d.display()
print()
d1.display()
d.concatenated(d1)
d.display()