[Python-3000] A minor cleanup: instances from bound methods

Tue Apr 18 11:02:15 CEST 2006

I noticed this the other day. Perhaps it is suitable for a python
3000 cleanup? It certainly seems illogical, but probably too
intrusive to change in python 2.x.
I needed to find the instance from a bound method, with obj.im_self.
Eg
 >>> class C(object):
 ... def fn(self): print "hello"
 ... 
 >>> c=C()
 >>> fn=c.fn
 >>> fn
 <bound method C.fn of <__main__.C object at 0xb7dd2acc>>
 >>> fn.im_self
 <__main__.C object at 0xb7dd2acc>
 >>> fn.__self__
 Traceback (most recent call last):
 File "<stdin>", line 1, in ?
 AttributeError: 'function' object has no attribute '__self__'
 >>>
But I discovered that builtin objects work in a completely different
way with obj.__self__, Eg
 >>> fd=open("myfile","w")
 >>> fn=fd.write
 >>> fn
 <built-in method write of file object at 0xb7dc1260>
 >>> fn.im_self
 Traceback (most recent call last):
 File "<stdin>", line 1, in ?
 AttributeError: 'builtin_function_or_method' object has no attribute 'im_self'
 >>> fn.__self__
 <open file 'myfile', mode 'w' at 0xb7dc1260>
 >>> 
I suggest that either im_self or __self__ is renamed!
-- 
Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick