Using my routines as functions AND methods

[Peter J. Holzer]

On 2024-01-03 23:17:34 -0500, Thomas Passin via Python-list wrote:
> On 1/3/2024 8:00 PM, Alan Gauld via Python-list wrote:
> > On 03/01/2024 22:47, Guenther Sohler via Python-list wrote:
> > > Hi,
> > > 
> > > In my cpython i have written quite some functions to modify "objects".
> > > and their python syntax is e.g.\
> > > 
> > > translate(obj, vec). e.g whereas obj is ALWAYS first argument.
                ^^^                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > 
> > > However, I also want to use these functions as class methods without having
> > > to
> > > write the function , twice. When using the SAME function as a methos, the
> > > args tuple must insert/contain "self" in the first location, so i have
> > > written a function to do that:
> > 
> > I'm probably missing something obvious here but can't you
> > just assign your function to a class member?
> > 
> > def myFunction(obj, ...): ...
                   ^^^
> > 
> > class MyClass:
> >      myMethod = myFunction
> > 
> > 
> > Then you can call it as
> > 
> > myObject = MyClass()
> > myObject.myMethod()
> > 
> > A naive example seems to work but I haven't tried anything
> > complex so there is probably a catch. But sometimes the simple
> > things just work?
> 
> That works if you assign the function to a class instance, but not if you
> assign it to a class.
> 
> def f1(x):
>     print(x)

You omitted the first argument (obj).

That should be 

def f1(obj, x):
    print(x)


> f1('The plain function')

> 
> class Class1:
>     pass

o = Class1()
f1(o, 'The plain function')

works for me.


> class Class2:
>     pass
> 
> c1 = Class1()
> c1.newfunc = f1
> c1.newfunc('f1 assigned to instance') # Works as intended

Now this doesn't work any more (but the OP doesn't want that anyway,
AFAICT).


> Class2.newfunc = f1
> c2 = Class2()
> c2.newfunc('f1 assigned to class')  # Complains about extra argument

But this does.

        hp

-- 
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp at hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"
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