CODEWITHSUNDEEP
pythonclassmethods
abc
abc

Reputation: 11949

__setattr__ vs class properties to set attributes

Consider the two following class definitions in which, in order to do additional checks before assigning a value to an attribute (e.g., keep track of modified variables, check for validity, etc.) in the first one I override the __setattr__ method and in the second one I use properties.

class A(object):
    def __init__(self, x):
        self.x = x

    def __setattr__(self, name, value):
        # do something
        self.__dict__[name] = value

class B(object):
    def __init__(self, x):
        self.x = x

    @property
    def x(self):
        return self.x

    @x.setter
    def x(self, v):
        # do something
        self.x = v

To me, it looks like they behave at the same way.
Is there any difference between the two? Which one should be preferred and why?

Upvotes: 2

Views: 87

Answers (1)

chepner
chepner

Reputation: 532238

__setattr__ is more general, as it will run for A().foo = 3, no matter what attribute foo you provide. Property setters are specific to a single, explicitly defined property, and can't be used to "accidentally" create an attribute.

Upvotes: 2

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