Manchester | 26-SDC-Jun | Fithi Teklom | Sprint 2 | LRU Cache in Python

Sprint-2/implement_lru_cache/linked_list.py

@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+from typing import Generic, TypeVar
+
+T = TypeVar("T")
+
+
+class Node(Generic[T]):
+    __slots__ = ("value", "next", "previous")
+
+    def __init__(self, value: T) -> None:
+        self.value: T = value
+        self.next: Node[T] | None = None
+        self.previous: Node[T] | None = None
+
+
+class LinkedList(Generic[T]):
+    def __init__(self) -> None:
+        self.head: Node[T] | None = None
+        self.tail: Node[T] | None = None
+
+    def push_head(self, value: T) -> Node[T]:
+        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.previous = new_node
+            self.head = new_node
+
+        return new_node
+
+    def pop_tail(self) -> T | None:
+        if self.tail is None:
+            return None
+
+        value = self.tail.value
+        self.remove(self.tail)
+        return value
+
+    def remove(self, node: Node[T]) -> None:
+        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
+
+    def move_to_head(self, node: Node[T]) -> None:
+        if node is self.head:
+            return
+
+        self.remove(node)
+
+        node.next = self.head
+        node.previous = None
+
+        if self.head is not None:
+            self.head.previous = node
+        else:
+            self.tail = node
+
+        self.head = node

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,32 @@
+from linked_list import LinkedList, Node
+class LruCache:
+    def __init__(self, limit: int) -> None:
+        if limit <= 0:
+            raise ValueError("Limit must be greater than zero")
+
+        self.limit: int = limit
+        self.cache: dict = {}
+        self.order: LinkedList[tuple] = LinkedList()
+
+    def get(self, key):
+        if key not in self.cache:
+            return None
+
+        node = self.cache[key]
+        self.order.move_to_head(node)
+
+        return node.value[1]
+
+    def set(self, key, value) -> None:
+        if key in self.cache:
+            node = self.cache[key]
+            node.value = (key, value)
+            self.order.move_to_head(node)
+            return
+
+        node = self.order.push_head((key, value))
+        self.cache[key] = node
+
+        if len(self.cache) > self.limit:
+            least_recent = self.order.pop_tail()
+            del self.cache[least_recent[0]]