import inspect
class Test(object):
    def test(self):
        pass
l = [123]
print inspect.ismethod(Test.test), type(Test.test)
print inspect.ismethod(l.append), type(l.append)

import inspect
 
#отсюда видно, что это лишь обёртка для встроенной функции isinstance()
def ismethod(object):
    """Return true if the object is an instance method.
  
    Instance method objects provide these attributes:
        __doc__         documentation string
        __name__        name with which this method was defined
        __func__        function object containing implementation of method
        __self__        instance to which this method is bound"""
    return isinstance(object, types.MethodType)
 
# но что такое types.MethodType ? смотрим в модуль types:
class _C:
    def _m(self): pass
  
MethodType = type(_C()._m)
 
# странно то, что для выражения inspect.ismethod(l.append) возвращается False! смотрим дальше:
l = [1, 2, 3]
print(type(l.append)) # <class 'builtin_function_or_method'>
  
# смотрим в модуль types:
BuiltinFunctionType = type(len)
BuiltinMethodType = type([].append)     # Same as BuiltinFunctionType
  
# смотрим в модуль inspect, какой же метод работает с этими типами:
def isbuiltin(object):
    """Return true if the object is a built-in function or method.
  
    Built-in functions and methods provide these attributes:
        __doc__         documentation string
        __name__        original name of this function or method
        __self__        instance to which a method is bound, or None"""
    return isinstance(object, types.BuiltinFunctionType)
  
# пробуем:
print(inspect.isbuiltin(l.append)) # True

>>> import types
>>> isinstance(len, types.BuiltinFunctionType)
True
>>> isinstance(len, types.BuiltinMethodType)
True
>>> isinstance([].append, types.BuiltinMethodType)
True
>>> isinstance([].append, types.BuiltinFunctionType)
True

class A:
     def func(self):
         pass
>>> A.func
<unbound method A.func>
>>> a = A()
>>> a.func
<bound method ...>
>>>inspect.ismethod(A.func)
True
>>>inspect.ismethod(a.func)
True

def ismethod(object):
    """Return true if the object is an instance method.
    Instance method objects provide these attributes:
        __doc__         documentation string
        __name__        name with which this method was defined
        im_class        class object in which this method belongs
        im_func         function object containing implementation of method
        im_self         instance to which this method is bound, or None"""
    return isinstance(object, types.MethodType)

UnboundMethodType = type(_C._m)         # Same as MethodType
_x = _C()
MethodType = type(_x._m)