Python decorate `class.method` that modify on `class.self`

Question

How to access self of the decorated method?

Based on this answer, the self refer to the decorator:

class Decorator:
    def __init__(self, func):
        self.func = func

    def __call__(self, *args, **kwargs):
        print(self.func.__name__)
        self.counter += 1
        return self.func(*args, **kwargs)


class A:
    def __init__(self):
        self.counter = 0
    @Decorator
    def method1(self):
        pass

Above example will cause:

      5 def __call__(self, *args, **kwargs):
----> 6     self.counter += 1
      7     return self.func(*args, **kwargs)

AttributeError: 'Decorator' object has no attribute 'counter'

NOTE:

The return self.func(*args, **kwargs) is also causing error. I don't yet fully understand how to pass that to A.method1. The point is just that I want to update counter and printing self.func.__name__, that is all.

in `__call__(self, ...)`,`self` points to the instance to which the method is bound, hence a instance of `Decorator`, not of `A` — cards, Feb 12 '23 at 01:45
@cards Yeah, I know that. The problem is I don't know how to access the A instance. — Muhammad Yasirroni, Feb 12 '23 at 01:58
@cards as long as it can update counter and access `method1.__name__` — Muhammad Yasirroni, Feb 12 '23 at 02:12

score 2 · Accepted Answer · edited Feb 12 '23 at 12:07

Here an example with a function-like decorator, it can be generalized with no afford to other cases.

Hint: when using class decorators use another identifier for the self of the other class, otherself, ...

def dec(f):
    def __wrapper(self, *args, **kwargs):
        self.counter += 1
        self.c.append(f.__name__)
        return f(self, *args, **kwargs)
    return __wrapper


class A:
    def __init__(self):
        self.counter = 0
        self.c = []

    @dec
    def method1(self):
        pass

a = A()
a.method1()
a.method1()
print(a.counter, a.c)
2 ['method1', 'method1']

Python decorate `class.method` that modify on `class.self`

1 Answers1