如何解决抽象类重写时的最大递归深度超限问题？

问题场景 #

尝试实现一个通过__getattribute__拦截方法调用，在方法执行前后触发before_execute和after_execute的抽象类，相关代码及运行错误如下：

父类定义 #

from abc import abstractmethod, ABC


class MethodInterceptor(object):

    @abstractmethod
    def before_execute(self):
        pass

    @abstractmethod
    def after_execute(self):
        pass

    def __getattribute__(self, name):
        attr = object.__getattribute__(self, name)
        if hasattr(attr, '__call__'):
            def new_func(*args, **kwargs):
                self.before_execute()

                result = attr(*args, **kwargs)
                self.after_execute()
                return result

            return new_func
        else:
            return attr

子类与业务类 #

class LoggerInterceptor(MethodInterceptor):
    def before_execute(self):
        print("before")

    def after_execute(self):
        print("after")


class Worker(LoggerInterceptor):
    def __init__(self):
        self.name = "worker"

    def work(self):
        print(f"hi I am {self.name}")


c = Worker()
c.work()

运行错误 #

Traceback (most recent call last):
  File "/Users/xxx/Projects/Pycharm/method_interceptor.py", line 47, in <module>
    c.work()
  File "/Users/xxx/Projects/Pycharm/method_interceptor.py", line 18, in new_func
    self.before_execute()
  File "/Users/xxx/Projects/Pycharm/method_interceptor.py", line 18, in new_func
    self.before_execute()
  File "/Users/xxx/Projects/Pycharm/method_interceptor.py", line 18, in new_func
    self.before_execute() 
  [Previous line repeated 996 more times]
RecursionError: maximum recursion depth exceeded

错误原因 #

__getattribute__会拦截所有属性和方法的访问请求，包括before_execute和after_execute。当包装后的work方法调用self.before_execute()时，又会触发__getattribute__，返回被包装后的before_execute方法；而这个包装后的方法内部又会再次调用self.before_execute()，形成无限递归，最终导致栈溢出。

解决方案 #

以下两种方式均可解决递归问题：

方式1：排除拦截钩子方法 #

修改__getattribute__，不对before_execute和after_execute进行包装，直接返回原始方法：

from abc import abstractmethod, ABC


class MethodInterceptor(object):

    @abstractmethod
    def before_execute(self):
        pass

    @abstractmethod
    def after_execute(self):
        pass

    def __getattribute__(self, name):
        attr = object.__getattribute__(self, name)
        # 仅对非钩子方法进行包装
        if hasattr(attr, '__call__') and name not in ('before_execute', 'after_execute'):
            def new_func(*args, **kwargs):
                self.before_execute()
                result = attr(*args, **kwargs)
                self.after_execute()
                return result

            return new_func
        else:
            return attr

方式2：直接获取原始钩子方法 #

在包装函数内部，通过object.__getattribute__直接获取未被包装的原始钩子方法，避免触发__getattribute__拦截：

from abc import abstractmethod, ABC


class MethodInterceptor(object):

    @abstractmethod
    def before_execute(self):
        pass

    @abstractmethod
    def after_execute(self):
        pass

    def __getattribute__(self, name):
        attr = object.__getattribute__(self, name)
        if hasattr(attr, '__call__'):
            def new_func(*args, **kwargs):
                # 直接获取原始方法，跳过拦截逻辑
                before = object.__getattribute__(self, 'before_execute')
                before()
                
                result = attr(*args, **kwargs)
                
                after = object.__getattribute__(self, 'after_execute')
                after()
                return result

            return new_func
        else:
            return attr

运行结果 #

修改后执行c.work()，会正常输出：

before
hi I am worker
after

内容的提问来源于stack exchange，提问作者barteloma