[Python] Dynamic read-only attributes in python instances

EDIT This code contains several bugs, see jsbueno's answer below for a correct version

I would like to create read-only attributes that dynamically retrieve values from an internal dictionary. I have tried to implement these as descriptors:

from typing import Any

class AttDesc:
def __init__(self, name):
self.name = name

def __get__(self, obj, objtype=None):
return obj._d[self.name]

def __set__(self, obj, value):
raise AtrributeError("Read only!")

class A:
def __init__(self, klist: list[str], vlist: list[Any]) -> None:
self._d = dict(zip(klist, vlist))
for k in self._d:
setattr(type(self), k, AttDesc(k))

@property
def d(self):
return self._d


The problem with this approach is that the descriptor instances are class attributes. This means that, in an interactive session:

a1 = A(['x', 'y'], [1, 2])
a2 = A(['z', ], [3])


if I press TAB for autocomplete on a1. I will be given the option to choose the attribute z, which "belongs" to instance a2. I have also tried to implement via the instance's __getattr__ method:

class B:
def __init__(self, klist: list[str], vlist: list[Any]):
object.__setattr__(self, '_d', dict(zip(klist, vlist)))

@property
def d(self):
return self._d

def __getattr__(self, name):
if name in self.d:
return self.d[name]
else:
object.__getattr__(name)

def __setattr__(self, k, v):
if k in self.d:
raise AttributeError("Read only!")
object.__setattr__(self, k, v)


If I try b = B(['w'], [3]) in an interactive session, pressing TAB on b. won't show w as an option, because it's not an instance attribute.

Pandas does something similar to what I want: it allows accessing the columns of a DataFrame with the dot operator, and only the appropriate columns for a given instance show up upon pressing TAB in an interactive session. I have tried to look into the Pandas code but it is a bit abstruse to me. I think they use something similar to my second __getattr__ option, but I don't understand how they make it work.

How could I implement this behaviour?

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