`obj[key]` is sugar for `obj.__getitem__(key)`. The first step is to look up the `__getitem__` method, and the second is to call it with the key. While it's possible that the code that raises the `TypeError` has access to all three objects, it can already be raised just by attempting `getattr(obj, '__getitem__')`, so I would not assume that this is a trivial thing to do at the level that the exception is being raised.
The traceback generator, on the other hand, has access to both the exception and the code objects that created it, which I suspect is why you are able to get the helpful underlines at that point. Also, note that reporting the key is also probably non-trivial. When it's a string or integer literal, that's one thing, but it could be an arbitrary expression that has up to that point not been evaluated. Attempting to execute it could trigger another exception, and attempting to report it could be quite long. Anyway, this is not a part of the code I've spent much time in, but I suspect it's not an easy QOL win. --- [Visit Topic](https://discuss.python.org/t/small-suggestion-regarding-type-errors-and-subscription/67898/15) or reply to this email to respond. You are receiving this because you enabled mailing list mode. To unsubscribe from these emails, [click here](https://discuss.python.org/email/unsubscribe/866906ba4030eeeba815a41997c217aa221ab9a14462d1bfd05ef48b2b4eef81).
