How can we control the sequence of function execution in Python Nose test

In a scenario of Nose tests in python

class test_class(testcase):
   def test_a(self):
      print 'test1'
   def test_b(self):
      print 'test2'
   def test_c(self):
      print 'test3'

when i execute the nosetest, the sequence of execution keep changing. Could some one please advise on how to provide/define a sequence for this execution.

Thanks so much in advance..

-Revant