用 Python 装饰一个类，打印装饰类的 int 变量

Question

I'm studying for a python course and one of the exercise was to create a decorator for this class that returns every int variables.`

@decoratoreDiClasse
class MyClass:
    def __init__(self):
        self.a = 1
        self.b = 2
        self.c = 'w'`

My problem is that the list is always empty beacuse dict does not return the variables inside init,how can i solve my problem? i've written my decorator below

def decoratoreDiClasse(cls):
def elencaVariabili():

    lista = []
    print(cls)
    lista1 = cls.__dict__
    print(lista1)

    for ab in lista1:

        if isinstance(ab, int):
            lista.append(ab)
    return lista

setattr(cls, "elencaVariabili", elencaVariabili())
return cls

here's the part of the main that should print the variables,I cannot change anything apart from "decoratoreDiClasse" due to the teacher request.

    for v in x.elencaVariabili():
    print(v, end=' ')

Answer 1

It looks like you're supposed to have your decorator add a method to the class that prints out integer-valued attributes on an instance it's called on. That's not what you're currently trying to do, as your code tries to find the variables on the class instead of on an instance later on.

Think of what you're doing as a method, and it will be a lot simpler:

def decoratoreDiClasse(cls):
    def elencaVariabili(self):     # this is a method, so it should take self!
        lista = [value for value in self.__dict__.values()  # loop over our attribute values
                       if isinstance(value, int)]           # and pick out the integers!
        return lista

    setattr(cls, "elencaVariabili", elencaVariabili)  # don't call the method here
    return cls

It's not entirely clear from your code if you're supposed to be returning the names of the integer variables or just the values themselves. I went with just the values, but if you need the variable names, you may need to change the list comprehension to iterate over the items() of the instance's dictionary rather than just the values() .