dynamically_add_methods.py

class T:
    ...

def _m(my): print('m', my)
T.m = _m

@classmethod
def _cm(cls): print('cm', cls)
T.cm = _cm
## ...OR
# def _cm(cls): print('cm', cls)
# T.cm = classmethod(cm)

def _sm(): print('sm')
T.sm = staticmethod(_sm)
# T.sm = _sm #=> Error!

t = T()

t.m()
T.m(t)

t.cm()
T.cm()
(T.cm)()
getattr(T, 'cm')()

t.sm()
T.sm()