implement LRU cache using OrderedDict

Was going to use my own linked list, this was easier.

Author: RaihanSharif

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,26 @@
+from collections import OrderedDict
+"""
+Was gonna implement my own using a dict to to store keys and
+my own doubly linked list to do the ordering. I'm not 100% sure about the complexity
+of the OrderedDict, but it should be O(1) for get and set. 
+"""
+
+class LruCache:
+    def __init__(self, limit):
+        if limit <= 0:
+            raise ValueError("Limit must be greater than 0")
+        self.limit = limit
+        self.data = OrderedDict()
+
+    def get(self, key):
+        if key not in self.data:
+            return None
+        self.data.move_to_end(key)    # end is most recent
+        return self.data[key]
+
+    def set(self, key, value):
+        if key in self.data:
+            self.data.move_to_end(key)
+        self.data[key] = value
+        if len(self.data) > self.limit:
+            self.data.popitem(last=False)