Setting a object property by variable ends up in an infinite loop [duplicate]

Question

I'm trying to create a simple model base

class Model:

    _fields = {}

    def __init__(self, **props):
        import pdb; pdb.set_trace()
        for key, value in props.items():
            if key in self._fields:
                setattr(self, key, value)

    def __setattr__(self, name, value):
        if name not in self._fields:
            return
        setattr(self, name, value)

However, when I set a value that is in my _fields list, it ends up in an infinite loop (setattr calling __setattr__). I can't figure out how I can set a value like this.

luther · Accepted Answer · 2019-08-27 02:28:59Z

0

To paraphrase the doc on __setattr__, if __setattr__ needs to set an attribute you can avoid recursion by calling the base class's __setattr__ method:

object.__setattr__(self, name, value)

# Or ...
super().__setattr__(self, name, value)

answered Aug 27, 2019 at 2:28

luther

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2 Comments

Rohit Over a year ago

Ah, so if this is inherited, I have to create a __setattr__ in each subclass? I can't just utilize it in the child?

luther Over a year ago

@Rohit: __setattr__ gets inherited like any other method. I'm not sure I understand your question. The point of this is that your __setattr__ must call a different __setattr__ in order to not be recursive.

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