Chanelling Guido - dict subclasses

[Tim Chase]

On 2014-01-15 01:27, Steven D'Aprano wrote:
> class TextOnlyDict(dict):
>     def __setitem__(self, key, value):
>         if not isinstance(key, str):
>             raise TypeError
>         super().__setitem__(key, value)
>     # need to override more methods too
> 
> 
> But reading Guido, I think he's saying that wouldn't be a good
> idea. I don't get it -- it's not a violation of the Liskov
> Substitution Principle, because it's more restrictive, not less.
> What am I missing?

Just as an observation, this seems almost exactly what anydbm does,
behaving like a dict (whether it inherits from dict, or just
duck-types like a dict), but with the limitation that keys/values need
to be strings.

-tkc