将装饰器应用于派生子类的所有方法

Question

我有一个非常通用的特定类，我想派生另一个类，其中一个命令在类方法之前运行。

我选择遵循的路径基于https://stackoverflow.com/a/55035043/1424118。我尝试了许多其他方法，但我感到自己了解其工作原理。好吧，这也是我的错。我的理解是，过程如下：1）创建一个子类，2）获取基类的所有可调用方法，3）用修饰后的版本覆盖这些方法。

我的代码是：

from functools import wraps, partial

def deco_func(func): #, channel):      
    @wraps(func)
    def new_function(*args,**kwargs):
        print("Decorator func.")
        return func(*args,**kwargs)                
    return new_function  

print("checking the operation of the decorator function")
def sq(a):
    print(a**2)
sq2 = deco_func(sq)
sq(1.1)
sq2(1.3) # yep, sq2 works


class my_class():
    def __init__(self, a):
        self.a = a
    def square(self):
        self.a = self.a**2
        print(self.a)

class my_subclass(my_class):
    def __init__(self, func, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # go over all elements in my_class and if it is callable, apply the
        # decorator function
        for attr_name in my_class.__dict__:
            attr = getattr(self, attr_name)
            if callable(attr) and a:
                print("Callable method found: %r" % attr_name)
                setattr(self, attr_name, partial(func, attr))

class my_subclass2(my_class):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # go over all elements in my_class and if it is callable, apply the
        # decorator function
        for attr_name in my_class.__dict__:
            attr = getattr(self, attr_name)
            if callable(attr) and a:
                print("Callable method found: %r" % attr_name)
                setattr(self, attr_name, partial(deco_func, attr))


print("\nOriginal class:")
a = my_class(1.05)
a.square()
a.square()
print("Supposed to be 1.05^4: %r" % a.a)
print("\nFirst subclass version:")
b = my_subclass(a=1.07, func=deco_func)
b.square()
b.square()
print("Supposed to be 1.07^4: %r" % b.a)
print("\nSecond subclass version:")
c = my_subclass2(a=1.03)
c.square()
c.square()
print("Supposed to be 1.03^4: %r" % c.a)

输出为：

checking the operation of the decorator function
1.2100000000000002
Decorator func.
1.6900000000000002

Original class:
1.1025
1.21550625
Supposed to be 1.05^4: 1.21550625

First subclass version:
Callable method found: '__init__'
Callable method found: 'square'
Supposed to be 1.07^4: 1.07

Second subclass version:
Callable method found: '__init__'
Callable method found: 'square'
Supposed to be 1.03^4: 1.03

问题是b.square()和c.square()返回一个函数对象，但我不明白为什么。我希望c.square（）与deco_func（my_class.square（））相同，后者为sq2（）。显而易见的问题是我在哪里错了，为什么修饰的类函数返回另一个函数，我又该如何解决这个问题？

我使用python 3.6.9。

Answer 1

以某种方式，函数partial（）破坏了代码。以下是有效的MWE。不幸的是，我无法向装饰器添加参数，但目前我可以接受。

from functools import wraps, partial
import inspect, types

def deco_func(func):       
    @wraps(func)
    def new_function(*args,**kwargs):
        print("Decorator func.")
        return func(*args,**kwargs)                
    return new_function  

class my_class():
    def __init__(self, a):
        self.a = a
    def square(self):
        self.a = self.a**2
        print(self.a)

class my_subclass(my_class):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        for attr_name in my_class.__dict__:
            attr = getattr(self, attr_name)
            if callable(attr) and attr_name[0:2] != "__":
                print("Callable method found: %r" % attr_name)
                setattr(self, attr_name, deco_func(attr))


print("\nOriginal class:")
a = my_class(1.02)
a.square()
a.square()
print("Supposed to be 1.02^4=1.082: %r" % a.a)

print("\nSubclass version:")
b = my_subclass(a=1.01)
b.square()
b.square()
print("Supposed to be 1.01^4=1.04: %r" % b.a)