London | 26-SDC-Mar | beko | Sprint 2 | implement a linked list in py…

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,62 @@
+from typing import Optional
+
+
+class _Node:
+    def __init__(self, value):
+        self.value = value
+        self.next: Optional["_Node"] = None
+        self.prev: Optional["_Node"] = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        new_node = _Node(value)
+
+        if self.head is None:
+            self.head = new_node
+            self.tail = new_node
+        else:
+            new_node.next  = self.head
+            self.head.prev = new_node
+            self.head      = new_node
+
+        return new_node
+
+    def pop_tail(self):
+        if self.tail is None:
+            return None
+
+        value = self.tail.value
+
+        if self.head == self.tail:
+            self.head = None
+            self.tail = None
+        else:
+            self.tail = self.tail.prev
+            if self.tail:
+                self.tail.next = None
+
+        return value
+
+    def remove(self, node):
+        if node == self.head:
+            self.head = node.next
+            if self.head:
+                self.head.prev = None
+            else:
+                self.tail = None
+
+        elif node == self.tail:
+            self.tail = node.prev
+            if self.tail:
+                self.tail.next = None
+            else:
+                self.head = None
+
+        else:
+            node.prev.next = node.next
+            node.next.prev = node.prev

Sprint-2/implement_linked_list/linked_list_test.py

@@ -32,7 +32,7 @@ def test_remove_tail(self):
         self.assertEqual(l.head, b)
         self.assertEqual(l.tail, b)
         self.assertIsNone(b.next)
-        self.assertIsNone(b.previous)
+        self.assertIsNone(b.prev)
 
 
 if __name__ == "__main__":