processing speed of instance variables and function arguments

I would recommend using timeit and not time for this:

import timeit class checkTime(): def __init__(self): self.a = 0 self.b = 0 self.c = 0 def printWithArgument(self,a,b,c): a+b+c def printWithSelf(self): self.a+self.b+self.c def getTime(self): def test1(): self.a = 1 self.b = 2 self.c = 3 self.printWithSelf() printWithSelf_elapsed_time = timeit.Timer(stmt=test1).repeat(number=100000) def test2(): self.printWithArgument(1,2,3) printWithArgument_elapsed_time = timeit.Timer(stmt=test2).repeat(number=100000) print ("printWithArgument_time:{0}".format(printWithArgument_elapsed_time) + "[sec]") print ("printWithSelf_time:{0}".format(printWithSelf_elapsed_time) + "[sec]") checkTime = checkTime() checkTime.getTime() 

Gives:

printWithArgument_time:[0.033693790435791016, 0.03463387489318848, 0.03436899185180664][sec] printWithSelf_time:[0.055680036544799805, 0.054234981536865234, 0.05341005325317383][sec] 

Arguments are about 40% faster than passing via instance variables. This is because that positional arguments can be passed and accessed without a dictionary lookup. Instance variables require a dictionary lookup on both assignment and access. This is also the reason why locals are faster than globals. Locals are stored in an array and accessed by index rather than in a dictionary indexed by name.