Added Doubly Linked List

lists/doublylinkedlist.py

@@ -0,0 +1,138 @@
+class doublylinkedlist:
+    class _Node:
+        __slots__ = '_data', '_prev', '_next'
+
+
+        def __init__(self, data, prev, next):
+            self._data = data
+            self._prev = prev
+            self._next = next
+
+
+    def __init__(self):
+        self._head = self._Node(None, None, None)
+        self._tail = self._Node(None, None, None)
+        self._tail._prev = self._head
+        self._head._next = self._tail
+        self._size = 0
+
+
+    def is_empty(self):
+        return self._size == 0
+
+
+    def add_first(self, value):
+        new_node = self._Node(value, None, None)
+        if self.is_empty():
+            self._head = new_node
+            self._tail = new_node
+        else:
+            new_node._next = self._head
+            self._head._prev = new_node
+        self._head = new_node
+        self._size += 1
+
+
+    def add_last(self, value):
+        new_node = self._Node(value, None, None)
+        if self.is_empty():
+            self._head = new_node
+            self._tail = new_node
+        else:
+            self._tail._next = new_node
+            new_node._prev = self._tail
+        self._tail = new_node
+        self._size += 1
+
+
+    def add_particular_position(self, value, position):
+        new_node = self._Node(value, None, None)
+        if self.is_empty():
+            self._head = new_node
+            self._tail = new_node
+        else:
+            temp = self._head
+            i = 1
+            while i < position-1:
+                temp = temp._next
+                i += 1
+            new_node._next = temp._next
+            new_node._prev = temp
+            temp._next._prev = new_node
+            temp._next = new_node
+        self._size += 1
+
+
+    def remove_first(self):
+        if self.is_empty():
+            print("The list is empty")
+        value = self._head._data
+        self._head = self._head._next
+        self._head._prev = None
+        self._size -= 1
+        if self.is_empty():
+            self._tail = None
+        return value
+
+
+    def remove_last(self):
+        if self.is_empty():
+            print("The list is empty")
+        value = self._tail._data
+        self._tail = self._tail._prev
+        self._tail._next = None
+        self._size -= 1
+        if self.is_empty():
+            self._head = None
+        return value
+
+
+    def remove_particular(self, position):
+        if self.is_empty():
+            print("The list is empty")
+        i = 1
+        temp = self._head
+        while i < position-1:
+            temp = temp._next
+            i += 1
+        value = temp._next._data
+        temp._next._next._prev = temp
+        temp._next = temp._next._next
+        self._size -= 1
+        return value
+
+
+    def print_forward(self):
+        temp = self._head
+        while temp:
+            print(temp._data, end='-->')
+            temp = temp._next
+        print()
+
+
+    def print_backward(self):
+        temp = self._tail
+        while temp:
+            print(temp._data, end='<--')
+            temp = temp._prev
+        print()
+
+
+dll = doublylinkedlist()
+dll.add_last(8)
+dll.add_first(2)
+dll.add_particular_position(3, 2)
+dll.add_first(1)
+dll.add_particular_position(5, 4)
+dll.add_particular_position(4, 4)
+dll.add_particular_position(6, 6)
+dll.add_particular_position(7, 7)
+dll.print_forward()
+dll.print_backward()
+print(dll.remove_last())
+print(dll.remove_first())
+dll.print_forward()
+dll.print_backward()
+print(dll.remove_particular(3))
+dll.print_forward()
+dll.print_backward()