Instance attributes vs method arguments

[John O'Hagan]

Is it better to do this:

class Class_a():
	def __init__(self, args):
		self.a = args.a		
		self.b = args.b
		self.c = args.c
		self.d = args.d
	def method_ab(self):
		return self.a + self.b
	def method_cd(self):		
		return self.c + self.d

or this:

class Class_b():
	def method_ab(self, args):
		a = args.a
		b = args.b
		return a + b
	def method_cd(self, args)	
		c = args.c
		d = args.d
		return c + d

?

Assuming we don't need access to the args from outside the class,
is there anything to be gained (or lost) by not initialising attributes that 
won't be used unless particular methods are called? 

Thanks,

John O'Hagan