Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56) 
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class A(object):
...   def a(self):
...     print 42
... 
>>> a = A()
>>> a.a
<bound method A.a of <__main__.A object at 0x7f7348182ad0>>
>>> dir(a.a)
['__call__', '__class__', '__cmp__', '__delattr__', '__doc__', '__format__', '__func__', '__get__', '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'im_class', 'im_func', 'im_self']
>>> type(a.a)
<type 'instancemethod'>
>>> def foo(self):
...   print 41
... 
>>> a.foo = foo
>>> type(a.foo); type(a.foo);
<type 'function'>
<type 'function'>
>>> a.foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() takes exactly 1 argument (0 given)
>>> a.foo(None)
41
>>> a.foo
<function foo at 0x7f7348171320>
>>>