Allow obj[key] to fallback to attribute-based __getitem__ #141980
Description
Feature or enhancement
Proposal:
In current Python, the expression:
obj[key]only works if the type defines a mapping or sequence slot.
If it does not, Python immediately raises TypeError, even if the object does provide a __getitem__ method dynamically.
This leads to surprising limitations for objects that delegate or map behavior to another object.
Example
Suppose we have an object acting as a dynamic view or proxy:
class ConfigView:
def __init__(self, target):
self.target = target
def __getattr__(self, name):
# forward lookups to the underlying object
return getattr(self.target, name)If the underlying object implements __getitem__, we would naturally expect:
view["path"]to work the same as:
view.target["path"]But currently it fails with:
TypeError: 'ConfigView' object is not subscriptable
even though __getitem__ is available via attribute lookup.
Proposal
When a type does not provide a mapping or sequence slot, allow obj[key] to fall back to an attribute lookup for __getitem__, following normal attribute resolution rules (__getattribute__, __getattr__, delegation, etc.).
This would make subscripting consistent with other special methods that already allow attribute-based fallback, and it would significantly improve the behavior of dynamic proxy objects.
I would like to hear thoughts on whether this fallback would be acceptable as an enhancement.
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
No response