implement linked list in python

Author: Faithy4444

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,50 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.previous = None  # renamed from prev
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        """Add element to start (O(1))"""
+        new_node = Node(value)
+        new_node.next = self.head
+
+        if self.head:
+            self.head.previous = new_node
+        else:
+            # If list was empty, tail is also the new node
+            self.tail = new_node
+
+        self.head = new_node
+        return new_node  # handle for later removal
+
+    def pop_tail(self):
+        """Remove element from end (O(1))"""
+        if not self.tail:
+            raise IndexError("pop_tail from empty list")
+
+        value = self.tail.value
+        self.remove(self.tail)
+        return value
+
+    def remove(self, node):
+        """Remove node (O(1)) using the handle"""
+        if node.previous:
+            node.previous.next = node.next
+        else:
+            # Node is head
+            self.head = node.next
+
+        if node.next:
+            node.next.previous = node.previous
+        else:
+            # Node is tail
+            self.tail = node.previous
+
+        node.previous = node.next = None