Null Design Pattern

Null.py

# Null Object Pattern 

class AbstractLogging:
	def Log(self, msg): 
		pass
	
from time import asctime, localtime
class RealLogging(AbstractLogging):
	def Log(self, msg):
		print 'Logged at', asctime(localtime()), msg

class NullLogging(AbstractLogging):    
	def Log(self, msg):
		return

# Proxy / wrapper around either null or real logger
class Logger:
	def __init__(self):
		self.On()
	def Log(self, msg):
		self.logger.Log(msg)
	def On(self):
		self.logger = RealLogging()
	def Off(self):
		self.logger = NullLogging()

Logger = Logger()

# Usage: 
class API:
	def doA(self):        
		Logger.Log('Am calling A')
		print 'A done.'
	def doB(self):
		Logger.Log('Am calling B')
		print 'B done.'

o = API()
o.doA()
o.doB()
Logger.Off()
o.doA()
o.doB()