# How to annotate a new "dict" class with TypedDict?

**URL:** <https://discuss.python.org/t/how-to-annotate-a-new-dict-class-with-typeddict/12723>\
**Category:** Python Help\
**Tags:** help, typing\
**Created:** [December 24, 2021, 1:40am UTC](https://discuss.python.org/t/how-to-annotate-a-new-dict-class-with-typeddict/12723 "2021-12-24T01:40:55Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![spoolar](https://avatars.discourse-cdn.com/v4/letter/s/cab0a1/32.png) [@spoolar](https://discuss.python.org/u/spoolar)\
**Post date:** [December 24, 2021, 1:40am UTC](https://discuss.python.org/t/how-to-annotate-a-new-dict-class-with-typeddict/12723/1 "2021-12-24T01:40:55Z")

</div>

I have the following classes:

```auto
from typing import Any, TypedDict

class RawDict(TypedDict):
    key1: str
    key2: int

class MyDict(dict):
    def __init__ (self, data: RawDict) -> None:
        self._validate(data)
        super(). __init__ (data)

    def _validate(self, data: RawDict) -> None:
        # validate data and raise if invalid

    def some_other_method(self) -> Any:
        # do anything interesting

```

I would like to be able to annotate every instance of `MyDict` with the `RawDict` type. Currently, it results in a typing error (MyPy 0.930):

```auto
var: RawDict = MyDict({"key1": "value", "key2": 1})
# error: Incompatible types in assignment (expression has type "MyDict", variable has type "RawDict")

```

On the other hand, if we annotate it with `MyDict`, we won’t know the exact types of values in that `dict`:

```auto
var: MyDict = MyDict({"key1": "value", "key2": 1})
var1 = var["key1"] # recognized as Any
var2 = var["key2"] # recognized as Any

```

In my actual implementation, the `RawDict` type is more complex, e.g. it’s keys are other `TypedDict`s or lists of `TypedDict`s.

How can I combine `MyDict` and `RawDict` so that my variables “know” about their actual keys and available methods?

I tried inheriting `class MyDict(RawDict):`, but it made MyPy fail with `error: Invalid statement in TypedDict definition; expected "field_name: field_type"`.

I’m using Python 3.8.