Family Day update

Task/Singleton/Python/singleton-3.py

@@ -0,0 +1,9 @@
+class Singleton(type):
+    _instances = {}
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]
+
+class Logger(object):
+    __metaclass__ = Singleton

Task/Singleton/Python/singleton-4.py

@@ -0,0 +1,2 @@
+class Logger(metaclass=Singleton):
+    pass