[Python-Dev] Draft proposal: Implicit self in Python 3.0 (original) (raw)

Jim Jewett jimjjewett at gmail.com
Fri Jan 6 20:14:21 CET 2006

Nick Coghlan wrote:

Eliminate the need for explicit class and self slots in class and instance methods by implicitly providing those slots on all functions.

How many positional arguments does the function have if I retrieve it from the class, rather than from an instance?

To keep things simple, it should have the same number of positional arguments no matter how you retrieve it -- think of self and cls as keyword arguments that we currently write in an odd manner.

class Foo: def init(x): # 1: Implicit self .x = x # 2: Brief form of: self.x = x def bar(a, b): # 3: Two arguments... print .x + a + b

f = Foo(10).bar # We agree this accepts 2 arguments f = Foo.bar # How many arguments does f accept? f = Foo.dict["bar"] # How many arguments does it accept now?

The answer to the first question has to be 3, or we lose too much functionality

No, it should be 2. If you use it as a staticmethod, there isn't any problem. If you really want a method outside of its context, then pass self (or cls) as a keyword.

f(4,5,self=Foo(10))

(I also think we could use class as the keyword, since class=expression is different from class Name: but that is a separate question.)

If you like having self at the front -- well, wasn't the "keywords must be last" restriction likely to go away even before python 3.0?

... a Java or C++ background where you can't manipulate functions and classes as first-class objects - the idea that the instance method signature could be written to describe the signature of the unbound method returned by "Foo.bar" rather than the bound method returned by "Foo().bar" is an entirely foreign concept.

I find it sort of strange that the signatures are different in the first place. I prefer the one without boilerplate.

-jJ

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