Using string formatting within class method docstrings

I have a class with several similar methods, each with long docstrings that are similar but vary with regards to several phrases/words. I'd like to build a docstring template and then apply string formatting to it. Below is a clumsy implementation where the __doc__s are defined after the class methods.

capture_doc = """
%(direc)s normal.

a %(sym)s b."""

class Cls():    
    def a(self):
        pass
    def b(self):
        pass
    a.__doc__ = capture_doc % {'direc' : 'below', 'sym' : '<'}     
    b.__doc__ = capture_doc % {'direc' : 'above', 'sym' : '>'}

c = Cls()    
print(c.a.__doc__)

below normal.

a < b.

Question: is there a Python docs- or PEP-prescribed way to do this? I'd like to keep things basic, I've seen use of an @Appender decorator but think that's a bit fancy for my needs.