kernel dies after @property in python

Question

I am running the following code in Jupyter:

from typing import List

class dummy:
    def __init__(self, dum: List =[]):
        self.dum = dum

    @property
    def dum(self) -> List:
        return self.dum

    @dum.setter
    def dum(self, value: List) -> None:
        self.dum = value

When I run the following:

dummy(dum=[1,2,3])

The kernel dies without telling me much about the possible error. What is going on?

Asked By: marcos

||

Source

Answer 1

@property
def dum(self) -> List:
    return self.dum

This creates an infinite recursion.

The attribute itself should have a different name. As per convention, it is usually the name of the property prefixed with an underscore.
While we are at it, default mutable arguments should be avoided.
mypy does not like implicit Optional annotations, so List = None should be Optional[List] = None.

from typing import List, Optional

class dummy:
    def __init__(self, dum: Optional[List] = None):
        self.dum = dum if dum is not None else []

    @property
    def dum(self) -> List:
        return self._dum

    @dum.setter
    def dum(self, value: List) -> None:
        self._dum = value

Answered By: DeepSpace

kernel dies after @property in python

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