如何通过 Decorator 在后台捕获 AttributeError？

Question

这会引发 AttributeError：

from functions import *

class Class:
    def __init__(self):
        self.name = 'Name'

    @exception_handler
    def do_stuff(self):
        print('Stuff')

if __name__ == '__main__':
    test = Class()
    test.dooo_stuff()

AttributeError: 'Class' object has no attribute 'dooo_stuff'

我想用后台装饰器以某种方式捕获此属性错误。这样我就可以通知用户 class 方法名称已更改。

所以

try:  
    test = Class()
    test.dooo_stuff()
except AttributeError:
    print('info')

将不起作用，因为它不在后台。我想更改上面的错误消息以通知用户。有什么办法吗？谢谢

Answer 1

Python Data Model is very powerfull. You can customize attribute access with the dunder method __getattr__ :

Called when the default attribute access fails with an AttributeError [...] This method should either return the (computed) attribute value or raise an AttributeError exception.

虽然通常的用法是提供动态值（例如 mock or defaultdict 就是这样实现的），但也可以执行我们想要的任何代码，例如调用回调 :

def handler(attribute_error_name):
    print(f"{attribute_error_name!r} does not exist")


class MyAPI:
    def do_stuff(self):
        return "done"

    def __getattr__(self, item):
        handler(item)
        return lambda: None  # if the return value is not callable, we get TypeError: 'NoneType' object is not callable

api = MyAPI()
print(api.do_stuff())
print(api.do_something_else())

产出

done
'do_something_else' does not exist
None

如何通过 Decorator 在后台捕获 AttributeError？

How to catch an AttributeError in Background through Decorator?

python

attributeerror