# PEP 728: TypedDict with Typed Extra Items

**URL:** <https://discuss.python.org/t/pep-728-typeddict-with-typed-extra-items/45443>\
**Category:** PEPs\
**Tags:** typing\
**Created:** [February 9, 2024, 5:20am UTC](https://discuss.python.org/t/pep-728-typeddict-with-typed-extra-items/45443 "2024-02-09T05:20:20Z")\
**Posts on this page:** 1\
**Showing post:** 115

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**Author:** ![JukkaL](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/jukkal/32/300_2.png) [@JukkaL](https://discuss.python.org/u/JukkaL)\
**Post date:** [October 3, 2024, 10:45am UTC](https://discuss.python.org/t/pep-728-typeddict-with-typed-extra-items/45443/115 "2024-10-03T10:45:06Z")

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> [@Jelle](#):
>
> This would conflict with TypedDicts that use `_` as a key (which feels a lot more likely than ` __extra_items__ `).

That’s fair, though `_` as a key is still probably quite rare. Your proposal seems pretty reasonable.

The issue with key conflicts got me thinking about a more general solution to work around key naming limitations. We already don’t support all possible keys when using the class-based syntax, and thus we probably can’t deprecate the functional syntax. What if we’d add a new way of specifying arbitrary string keys using the class-based-syntax? Here’s one idea:

```py
class Foo(TypedDict):
    name: str # Regular item
    _: bool # Type of extra items
    __items__ = {
        "_": int, # Literal "_" as a key
        "class": str, # Keyword as a key
        "tricky.name?": float, # Arbitrary str key
    }

```

(The name ` __items__ ` is just the first thing that came to my mind – the specifics of the name aren’t important.)

This may go beyond the original goals of the PEP, but this would have some nice properties:

- Arbitrary key names can be supported using the class-based syntax.
- We can hopefully deprecate the functional TypedDict syntax.
- We can support forward references in the extra item type without escaping.
- All TypedDict items (including the extra ones) are defined using a similar syntax in the common case where ` __items__ ` is not needed.
- We have the option of adding arbitrary magic key names such as `_`, since name conflicts can be worked around easily.

This would make the proposal a bit bigger, but on the other hand, we could deprecate the functional syntax, so arguably this would simplify the overall non-deprecated TypedDict functionality.

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