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

ntoronto at cs.byu.edu ntoronto at cs.byu.edu
Tue Nov 20 09:50:47 CET 2007

> Neil Toronto wrote:
>> Because the runtime enforces isinstance(D_instance, D), everything else
>> can be handled with D_instance.method(...) or self.method() or
>> super.method().
> But super() is not a general replacement for explicit inherited
> method calls. It's only appropriate in special, quite restricted
> circumstances.

Exactly. There are two common method-calling cases, and an uncommon one.
In order of expected number of occurrences, with #3 being quite low:

1. self.method(...)

2. super.method(...)

3. DistantParent.method(self, ...) (either to get out of the MRO or
because you're feeling evil - two use cases for it)

If self were only implicitly available, #3 would need a new spelling, as
you say. That's not hard to do, and I've already suggested
as_parent(DistantParent, self).method(...) as an alternate spelling for
the uncommon cases.

That's not to say I'm advocating such a thing for Python 3.0 - just
showing that it's possible to cover the current known use cases. Actually,
I suspect there aren't any more use cases, as all correct ways of calling
the method (those that don't raise an exception) are covered, and implicit
self would still be as accessible from anywhere as explicit self is.

Would saving six keystrokes per method, reducing noise in every method
header, and removing the need for a habit (always including self in the
parameter list) be enough to justify a change? I'm going to guess either
"no" or "not right now". If I were doing it from scratch, I'd make self
and super into keywords, and change method binding to return a function
with them included in the locals somehow.


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