How to get instance variables in Python?

Is there a built-in method in Python to get an array of all a class' instance variables? For example, if I have this code:

class hi:
  def __init__(self):
    self.ii = "foo"
    self.kk = "bar"

Is there a way for me to do this:

>>> mystery_method(hi)
["ii", "kk"]

Edit: I originally had asked for class variables erroneously.