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Allow use of `Required` and `NotRequired` to make an existing typed dict total or optional

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#1,454 8 comments 7 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
developer-experience

Research direction

Start by reviewing the proposed TypedDict, Required, and NotRequired semantics and the examples in the issue, including inheritance and inline annotations. Define the behavior and identify the relevant typing specification and conformance tests; done means the requested transformations are specified and validated consistently.

Written by the indexing model from the issue text.

Description

topic: feature

I think the ability of indicating that a typed dict requires all keys or that all are optional would be very useful.

For example to allow defining default values for a particular dict or to return a dict that has been completely assigned from a function

A simple example

class A(TypedDict):
    a: int
    b: int

ADefault = {'a': 1, 'b': 42}

def optionalA(v: NotRequired[A]) -> A:
    return ADefault | v

optionalA({'a': 11}) # ok since all keys of NotRequired[A] are optional

class X(TypedDict, total=False):
    x: str
    y: str

XDefault: X = {"x": "xv", "y": "yv"}

def withXDefault(v: X) -> Required[X]:
    return XDefault | v

withXDefault({"x": "foo"})["y"]  # ok since all keys of Required[X] are required

This idea is inspired by the analogous types in typescript Required and Partial that are in general very convenient.

I think it makes sense having the same behaviour of the typescript counterparts:

  • NotRequired[X] is a no op, since X is defined as total=False. Same for Required[A].
  • Required/NotRequired would include all keys of the typed dict and all its superclasses. This differs from how total works. Example: 
    class TD1(TypedDict):
    a: int

class TD2(TypedDict, total=False):
    b: int

TDR = Required[TD2]  # b becomes required
TDNR = NotRequired[TD2]  # a becomes not required
  • Required/NotRequired used inline in the TypedDict are not taken into consideration, so the end result is the same independently of how the typed dict is defined
Dominant language
Python
Stars
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Forks
302
Avg merge
23h
Merged PRs (30d)
8

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  1. Read the whole issue, then the project's contributing guide.
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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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