[Python-ideas] Explicit self argument, implicit super argument

Neil Toronto ntoronto at cs.byu.edu
Mon Nov 19 20:00:04 CET 2007

(Disclaimer: I have no issue with "self." and "super." attribute access, 
which is what most people think of when they think "implicit self".)

While showing a coworker a bytecode hack I made this weekend - it allows 
insertion of arbitrary function parameters into an already-existing 
function - he asked for a use case. I gave him this:

class A(object):
     # ...
     def method(x, y):
         self.x = x

where 'method' is replaced by this method wrapper via metaclass or 

def method_wrapper(self, *args, **kwargs):
     return hacked_method(self, super(cls, self), *args, **kwargs)

These hackish details aren't important, the resulting "A.method" is.

It occurred to me that explicit self and implicit super is semantically 
inconsistent. Here's Python 3000's version of the above (please compare):

class A(object):
     def method(self, x, y):
         self.x = x

Why have a magic "super" local but not a magic "self" local? From a 
*general usage* standpoint, the only reason I can think of (which is not 
necessarily the only one, which is why I'm asking) is that a person 
might want to change the name of "self", like so:

class AddLike(object):
     # ...
     def __add__(a, b):
         # return something
     def __radd__(b, a):
         # return something

But reverse binary special methods are the only case where it's not 
extremely bad form. Okay, two reasons for explicit self: backward 
compatibility, but 2to3 would make it a non-issue.

 From an *implementation standpoint*, making self implicit - a cell 
variable like super, for example - would wreak havoc with the current 
bound/unbound method distinction, but I'm not so sure that's a bad thing.


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