Implemented Singleton metaclass

patterns/creational.py

@@ -1,4 +1,19 @@
 
 
-class Singleton(object):
-    pass
+class Singleton(type):
+    """
+    Singleton Metaclass.
+
+    Enforces any object using this metaclass to only create a single instance.
+    """
+    __instance = None
+
+    def __call__(cls, *args, **kwargs):
+        """
+        Override the __call__ method to make sure only one instance is created.
+        """
+        if cls.__instance is None:
+            cls.__instance = type.__call__(cls, *args, **kwargs)
+
+        return cls.__instance
+