[Python-ideas] Define a method or function attribute outside of a class with the dot operator

Stephan Houben stephanh42 at gmail.com
Fri Feb 10 05:29:32 EST 2017

What about using a simple decorator instead?

def monkey_patch(cls):
    return lambda func: setattr(cls, func.__name__, func)

class Foo:

def bar(self):
    return 42

# gives 42

2017-02-10 11:15 GMT+01:00 Matthias welp <boekewurm at gmail.com>:

> Hi Markus,
> Thanks for writing this up, as I've had this same very valid problem
> before.
> On 10 February 2017 at 10:13, Markus Meskanen <markusmeskanen at gmail.com>
> wrote:
> > I'm suggesting the addition of support to using a dot notation when
> defining
> > a function to be a method of a class, or a callback attribute.
> Your solution to me seems like a 'hack': class monkey-patching during
> runtime
> is already available if you really need it, and your proposal only
> makes it easier,
> which I don't really like.
> > This functionality would be useful in the few rare cases where the class
> > itself needs to be accessed in the function's definition (decorator,
> typing,
> > etc
> This problem could just as well be solved by allowing access to a
> scope-level
> variable (__class__? __type__?) which is available in the class body at
> construction time, which points to the (eventual) class type object,
> or evaluating
> the type hints in a class only after the class is created, which then
> allows for that
> class to be pointed to in the type annotations.
> E.G. this does not work right now:
>     class A:
>         def foo(self: A):
>             pass
> as it fails with NameError: A is not defined, whereas you'd expect it to
> work.
> The problem is very annoying when you're trying to work with the dunder
> methods for e.g. numerical objects, as you cannot say '+ is only allowed
> for
> these types', but it is not limited to this scope only.
> -Matthias
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