The Python 3.15 improved error message for nested attribute access doesn't seem to work on properties.
Rationale
Take the example from the What's new in Python 3.15 docs:
from dataclasses import dataclass
@dataclass
class Circle :
radius : float
@property
def area (self ) -> float :
return pi * self .radius ** 2
class Container :
def __init__ (self , inner : Circle ) -> None :
self .inner = inner
circle = Circle (radius = 4.0 )
container = Container (circle )
print (container .area )Running it with the CPython main branch or Python 3.15.0a1 through Python 3.15.0a7 (with uv) produces the following error:
Traceback (most recent call last ):
File "/Users/rodrigogs/Documents/cpython/../tmp/circle.py" , line 17 , in < module >
print (container .area )
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
AttributeError : 'Container' object has no attribute 'area' If you remove @property or if you try accessing container.radius instead, you get the respective improved messages:
# After removing `@property` from `area`:
Traceback (most recent call last ):
File "/Users/rodrigogs/Documents/cpython/../tmp/circle_no_prop.py" , line 16 , in < module >
print (container .area )
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
AttributeError : 'Container' object has no attribute 'area' . Did you mean : 'inner.area' ?
# ---
# Accessing `radius` instead of the property `area`:
Traceback (most recent call last ):
File "/Users/rodrigogs/Documents/cpython/../tmp/circle_radius.py" , line 17 , in < module >
print (container .radius )
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
AttributeError : 'Container' object has no attribute 'radius' . Did you mean : 'inner.radius' ?Helper scripts for easier testing
circle.py — original example that doesn't workfrom dataclasses import dataclass
@dataclass
class Circle :
radius : float
@property
def area (self ) -> float :
return pi * self .radius ** 2
class Container :
def __init__ (self , inner : Circle ) -> None :
self .inner = inner
circle = Circle (radius = 4.0 )
container = Container (circle )
print (container .area )
circle_radius.py — accessing radius worksfrom dataclasses import dataclass
@dataclass
class Circle :
radius : float
@property
def area (self ) -> float :
return pi * self .radius ** 2
class Container :
def __init__ (self , inner : Circle ) -> None :
self .inner = inner
circle = Circle (radius = 4.0 )
container = Container (circle )
print (container .radius )
circle_no_prop.py — removing the property worksfrom dataclasses import dataclass
@dataclass
class Circle :
radius : float
# @property
def area (self ) -> float :
return pi * self .radius ** 2
class Container :
def __init__ (self , inner : Circle ) -> None :
self .inner = inner
circle = Circle (radius = 4.0 )
container = Container (circle )
print (container .area )
CPython versions tested on:
3.15, CPython main branch
Operating systems tested on:
macOS
Linked PRs
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The Python 3.15 improved error message for nested attribute access doesn't seem to work on properties.
Rationale
Take the example from the What's new in Python 3.15 docs:
Running it with the CPython main branch or Python 3.15.0a1 through Python 3.15.0a7 (with uv) produces the following error:
If you remove
@propertyor if you try accessingcontainer.radiusinstead, you get the respective improved messages:Helper scripts for easier testing
circle.py— original example that doesn't workcircle_radius.py— accessing radius workscircle_no_prop.py— removing the property worksCPython versions tested on:
3.15, CPython main branch
Operating systems tested on:
macOS
Linked PRs