Data commit

Task/Singleton/Python/singleton-2.py

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+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