refactored a method to move a node to front, and added slots

Author: TzeMingHo

Sprint-2/implement_lru_cache/linked_list.py

@@ -1,11 +1,15 @@
 class Node:
+    __slots__ = ("key", "value", "previous", "next")
+
     def __init__(self, key, value):
         self.key = key
         self.value = value
         self.previous = None
         self.next = None
 
 class LinkedList:
+    __slots__ = ("head", "tail")
+
     def __init__(self):
         self.head = None
         self.tail = None
@@ -33,7 +37,7 @@ def pop_tail(self):
 
     def remove(self, node):
         if self.head == None and self.tail == None:
-            return
+            return None
 
         new_previous = node.previous
         new_next = node.next
@@ -66,4 +70,4 @@ def push_tail(self, new_node):
             self.tail.next = new_node
             new_node.previous = self.tail
             self.tail = new_node
-        return new_node
+        return new_node

Sprint-2/implement_lru_cache/lru_cache.py

@@ -1,6 +1,8 @@
 from linked_list import LinkedList, Node
 
 class LruCache:
+    __slots__ = ("limit", "dict", "linked_list")
+
     def __init__(self, limit):
         if limit <= 0:
             raise ValueError("limit must be positive")
@@ -12,18 +14,21 @@ def get(self, key):
         if key not in self.dict:
             return None
         else:
-            most_recent_node = self.linked_list.remove(self.dict[key])
-            self.linked_list.push_head(most_recent_node)
-            return most_recent_node.value
+            return self.move_to_front(self.dict[key]).value
 
     def set(self, key, value):
         if key in self.dict:
             self.dict[key].value = value
-            self.get(key)
+            self.move_to_front(self.dict[key])
         else:
             if len(self.dict) == self.limit:
                 removed_node = self.linked_list.pop_tail()
                 del self.dict[removed_node.key]
             self.dict[key] = Node(key, value)
             self.linked_list.push_head(self.dict[key])
+
+    def move_to_front(self, node):
+        most_recent_node = self.linked_list.remove(node)
+        self.linked_list.push_head(most_recent_node)
+        return most_recent_node