diff --git a/tools/tools.py b/tools/tools.py
index eec7dcf..ec386c9 100644
--- a/tools/tools.py
+++ b/tools/tools.py
@@ -7,6 +7,25 @@ from functools import wraps
 from typing import Any
 
 
+class Cache(dict):
+    def __init__(self):
+        super().__init__()
+        self.hits = 0
+        self.misses = 0
+
+    def str_hits(self) -> str:
+        return "%d (%1.2f)" % (self.hits, self.hits / (self.misses + self.hits) * 100)
+
+    def __contains__(self, item: Any) -> bool:
+        r = super().__contains__(item)
+        if r:
+            self.hits += 1
+        else:
+            self.misses += 1
+
+        return r
+
+
 def get_script_dir(follow_symlinks: bool = True) -> str:
     """return path of the executed script"""
     if getattr(sys, 'frozen', False):