Python TypedDict

from typing import TypedDict

class Student(TypedDict):
	grade: int
	name: str

student: Student = { "grade": 1, "name": "tonynamy" }
student = Student(grade=1, name="tonynamy")
student = Student({ "grade": 1, "name": "tonynamy" })

>>> import inspect
	from typing import TypedDict
	print(inspect.getsource(TypedDict))

def TypedDict(typename, fields=None, /, *, total=True, **kwargs):
    """A simple typed namespace. At runtime it is equivalent to a plain dict.

    TypedDict creates a dictionary type such that a type checker will expect all
    instances to have a certain set of keys, where each key is
    associated with a value of a consistent type. This expectation
    is not checked at runtime.

    Usage::

        class Point2D(TypedDict):
            x: int
            y: int
            label: str

        a: Point2D = {'x': 1, 'y': 2, 'label': 'good'}  # OK
        b: Point2D = {'z': 3, 'label': 'bad'}           # Fails type check

        assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first')

    The type info can be accessed via the Point2D.__annotations__ dict, and
    the Point2D.__required_keys__ and Point2D.__optional_keys__ frozensets.
    TypedDict supports an additional equivalent form::

        Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})

    By default, all keys must be present in a TypedDict. It is possible
    to override this by specifying totality::

        class Point2D(TypedDict, total=False):
            x: int
            y: int

    This means that a Point2D TypedDict can have any of the keys omitted. A type
    checker is only expected to support a literal False or True as the value of
    the total argument. True is the default, and makes all items defined in the
    class body be required.

    The Required and NotRequired special forms can also be used to mark
    individual keys as being required or not required::

        class Point2D(TypedDict):
            x: int               # the "x" key must always be present (Required is the default)
            y: NotRequired[int]  # the "y" key can be omitted

    See PEP 655 for more details on Required and NotRequired.
    """
    if fields is None:
        fields = kwargs
    elif kwargs:
        raise TypeError("TypedDict takes either a dict or keyword arguments,"
                        " but not both")
    if kwargs:
        warnings.warn(
            "The kwargs-based syntax for TypedDict definitions is deprecated "
            "in Python 3.11, will be removed in Python 3.13, and may not be "
            "understood by third-party type checkers.",
            DeprecationWarning,
            stacklevel=2,
        )

    ns = {'__annotations__': dict(fields)}
    module = _caller()
    if module is not None:
        # Setting correct module is necessary to make typed dict classes pickleable.
        ns['__module__'] = module

    return _TypedDictMeta(typename, (), ns, total=total)

{'grade': <class 'int'>, 'name': <class 'str'>}
>>> Student.__required_keys__
frozenset({'name', 'grade'})
>>> Student.__optional_keys__
frozenset()

import datetime
from typing import NotRequired, TypedDict

class Student(TypedDict):
	grade: int
	name: str
	graduated_at: NotRequired[datetime.datetime]

student = Student({ # OK
	"grade": 1,
	"name": "tonynamy",
	"graduated_at": datetime.datetime(2023, 2, 14)
})
student = Student({ # Also OK
	"grade": 1,
	"name": "tonynamy",
})

>>> Student.__required_keys__
frozenset({'name', 'grade'})
>>> Student.__optional_keys__
frozenset({'graduated_at'})

>>> import inspect
	from typing import _TypedDictMeta
	print(inspect.getsource(_TypedDictMeta))

class _TypedDictMeta(type):
    def __new__(cls, name, bases, ns, total=True):
        """Create a new typed dict class object.

        This method is called when TypedDict is subclassed,
        or when TypedDict is instantiated. This way
        TypedDict supports all three syntax forms described in its docstring.
        Subclasses and instances of TypedDict return actual dictionaries.
        """
        for base in bases:
            if type(base) is not _TypedDictMeta and base is not Generic:
                raise TypeError('cannot inherit from both a TypedDict type '
                                'and a non-TypedDict base class')

        if any(issubclass(b, Generic) for b in bases):
            generic_base = (Generic,)
        else:
            generic_base = ()

        tp_dict = type.__new__(_TypedDictMeta, name, (*generic_base, dict), ns)

        annotations = {}
        own_annotations = ns.get('__annotations__', {})
        msg = "TypedDict('Name', {f0: t0, f1: t1, ...}); each t must be a type"
        own_annotations = {
            n: _type_check(tp, msg, module=tp_dict.__module__)
            for n, tp in own_annotations.items()
        }
        required_keys = set()
        optional_keys = set()

        for base in bases:
            annotations.update(base.__dict__.get('__annotations__', {}))
            required_keys.update(base.__dict__.get('__required_keys__', ()))
            optional_keys.update(base.__dict__.get('__optional_keys__', ()))

        annotations.update(own_annotations)
        for annotation_key, annotation_type in own_annotations.items():
            annotation_origin = get_origin(annotation_type)
            if annotation_origin is Annotated:
                annotation_args = get_args(annotation_type)
                if annotation_args:
                    annotation_type = annotation_args[0]
                    annotation_origin = get_origin(annotation_type)

            if annotation_origin is Required:
                required_keys.add(annotation_key)
            elif annotation_origin is NotRequired:
                optional_keys.add(annotation_key)
            elif total:
                required_keys.add(annotation_key)
            else:
                optional_keys.add(annotation_key)

        tp_dict.__annotations__ = annotations
        tp_dict.__required_keys__ = frozenset(required_keys)
        tp_dict.__optional_keys__ = frozenset(optional_keys)
        if not hasattr(tp_dict, '__total__'):
            tp_dict.__total__ = total
        return tp_dict

    __call__ = dict  # static method

    def __subclasscheck__(cls, other):
        # Typed dicts are only for static structural subtyping.
        raise TypeError('TypedDict does not support instance and class checks')

    __instancecheck__ = __subclasscheck__

if annotation_origin is Required:
	required_keys.add(annotation_key)
elif annotation_origin is NotRequired:
	optional_keys.add(annotation_key)
elif total:
	required_keys.add(annotation_key)
else:
	optional_keys.add(annotation_key)

# `total=True`
>>> class Student(TypedDict, total=True):
...     grade: int
...     name: str
...
>>> Student.__required_keys__
frozenset({'name', 'grade'})
>>> Student.__optional_keys__
frozenset()

# `total=False`
>>> class Student(TypedDict, total=False):
...     grade: int
...     name: str
...
>>> Student.__required_keys__
frozenset()
>>> Student.__optional_keys__
frozenset({'name', 'grade'})

>>> from typing import Required
>>> class Student(TypedDict, total=False):
...     grade: Required[int]
...     name: str
>>> Student.__required_keys__