0 
class Foo:
    def __init__(self, data: list):
        self._data = data
    
    @property
    def data(self):
        return self._data

Doing this prevents from assignments like obj.data = [1, 2, 3], but it is still possible to modify it with obj.data.append(10) because lists are mutable. There's no problem for being able to modify it from obj._data, but I don't want it to be mutable from obj.data.

One thing I tried is making a copy of _data and then returning it

class Foo:
    def __init__(self, data: list):
        self._data = data
    
    @property
    def data(self):
        copy = self._data[:]
        return copy

but I'm not sure if this is the best way to do it, are there any other alternative ways?

Improve this question
8
  • "best way" measured how? Commented Oct 5, 2023 at 17:58
  • 1
    You can use tuple instead of a list. Commented Oct 5, 2023 at 17:58
  • if you are using a list, it will be mutable. There is nothing you can do to change that. You can, of course, use something other than a list, or return a copy like you have in the question Commented Oct 5, 2023 at 18:02
  • @ScottHunter whatever is considered best practice Commented Oct 5, 2023 at 18:05
  • @AndrejKesely what if it's a dict? Commented Oct 5, 2023 at 18:05
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