Data commit

Task/Singleton/Python/singleton-1.py

@@ -0,0 +1,19 @@
+>>> class Borg(object):
+	__state = {}
+	def __init__(self):
+		self.__dict__ = self.__state
+	# Any other class names/methods
+
+	
+>>> b1 = Borg()
+>>> b2 = Borg()
+>>> b1 is b2
+False
+>>> b1.datum = range(5)
+>>> b1.datum
+[0, 1, 2, 3, 4]
+>>> b2.datum
+[0, 1, 2, 3, 4]
+>>> b1.datum is b2.datum
+True
+>>> # For any datum!

Task/Singleton/Python/singleton-2.py

@@ -0,0 +1,29 @@
+import abc
+
+class Singleton(object):
+    """
+    Singleton class implementation
+    """
+    __metaclass__ = abc.ABCMeta
+
+    state = 1 #class attribute to be used as the singleton's attribute
+
+    @abc.abstractmethod
+    def __init__(self):
+        pass #this prevents instantiation!
+
+    @classmethod
+    def printSelf(cls):
+        print cls.state #prints out the value of the singleton's state
+
+#demonstration
+if __name__ == "__main__":
+    try:
+        a = Singleton() #instantiation will fail!
+    except TypeError as err:
+        print err
+    Singleton.printSelf()
+    print Singleton.state
+    Singleton.state = 2
+    Singleton.printSelf()
+    print Singleton.state

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