CODEWITHSUNDEEP
python
JokerMartini
JokerMartini

Reputation: 6147

python: set read-only attribute for class objects

I've created a class object called 'Node'. I then created two subclasses 'Beetle' and 'Dakota'. You'll notice there is an attr called 'superclass' which is part of the baseclass. I want this attribute to be set for each subclass and once it's set it should never be changed. It's a read-only attribute. I was wondering how to set this attribute up correctly in order to be a read only attribute?

class Node(object):
    def __init__(self, name, superclass, attributes, children):
        self.name = name
        self.superclass = superclass
        self.attributes = attributes if attributes is not None else {}
        self.children = children if children is not None else []


    class Beetle(Node):
        def __init__(self, name="", superclass="Cars", attributes=None, children=None, enabled=True):
            super(Beetle, self).__init__(name=name, superclass=superclass, attributes=attributes, children=children)
            self.enabled = enabled


    class Dakota(Node):
        def __init__(self, name="", superclass="Trucks", attributes=None, children=None, enabled=True):
            super(Dakota, self).__init__(name=name, superclass=superclass, attributes=attributes, children=children)
            self.enabled = enabled

Upvotes: 3

Views: 1379

Answers (2)

mattgathu
mattgathu

Reputation: 1147

To have a 'read-only' property in a class you can make use of the @property decoration.

An example:

class Dakota(object):
def __init__(self, superclass):
    self.__superclass = superclass

    @property
    def superclass(self):
        return self.__superclass

Usage:

>>> a = Dakota('lol')
>>> a.superclass
'lol'
>>> a.superclass = 'hah'
AttributeError...    

AttributeError: can't set attribute

You can refer to this other answer thread

Upvotes: 2

Kenly
Kenly

Reputation: 26688

Rename you variable to add __ to the begining

self.__superclass = superclass

you can't access self.__superclass with something like Dakota().__superclass

if you want to get value of __superclass add a function in Node class to return it.

def getsuperclass(self):
    return self.__superclass
...

Dakota().getsuperclass()

Upvotes: 1

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