implemented linked_list.py

Author: M-Abdoon

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,53 @@
+class Node:
+    __slots__ = ('value', 'next', 'previous')
+
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+        self.previous = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        node = Node(value)
+        if self.head is None:
+            self.head = node
+            self.tail = node
+        else:
+            node.next = self.head
+            self.head.previous = node
+            self.head = node
+        return node
+
+    def pop_tail(self):
+        if self.tail is None:
+            raise IndexError('pop from empty list')
+        node = self.tail
+        value = node.value
+        if node.previous is None:
+            self.head = None
+            self.tail = None
+        else:
+            self.tail = node.previous
+            self.tail.next = None
+            node.previous = None
+        node.next = None
+        return value
+
+    def remove(self, node):
+        if node.previous is not None:
+            node.previous.next = node.next
+        else:
+            self.head = node.next
+
+        if node.next is not None:
+            node.next.previous = node.previous
+        else:
+            self.tail = node.previous
+
+        node.next = None
+        node.previous = None