Pydantic Partial Model

partial.py

from copy import copy
from typing import Generic, Optional, TypeVar, get_args, get_type_hints

from pydantic import BaseModel
from pydantic.errors import ConfigError
from pydantic.typing import convert_generics

T = TypeVar('T', bound=BaseModel)


class Partial(Generic[T], BaseModel):
    class Config:
        abstract = True

    def __init_subclass__(cls, *args, **kwargs):
        orig_bases = getattr(cls, '__orig_bases__')
        base_class = get_args(orig_bases[0])[0]
        base_fields = base_class.__fields__
        type_hints = get_type_hints(base_class)

        config = getattr(cls, 'Config', None)
        includes = getattr(config, 'include', [])
        excludes = getattr(config, 'exclude', [])
        if includes and excludes:
            raise ConfigError('include and exclude are mutually exclusive')

        field_names = set(base_fields.keys())
        if includes and set(includes) - field_names:
            raise ConfigError(f'{includes[0]} is not a valid field name')
        if excludes and set(excludes) - field_names:
            raise ConfigError(f'{excludes[0]} is not a valid field name')

        for name, field in base_fields.items():
            if includes and name not in includes:
                continue
            if excludes and name in excludes:
                continue

            optional_field = copy(field)
            if field.required:
                optional_field.required = False
                optional_field.allow_none = True
                if getattr(optional_field, 'default_factory', None):
                    optional_field.default_factory = lambda: None
                else:
                    optional_field.default = None

            cls.__fields__[name] = optional_field
            cls.__annotations__[name] = Optional[type_hints[name]]

        if not cls.__doc__:
            cls.__doc__ = base_class.__doc__ or ''

partial_example.py

from pydantic import BaseModel


class Item(BaseModel):
    a: str
    b: int
    c: str
    d: int


class UpdateItemInput(Partial[Item]):
    class Config:
        include = ['a', 'b']
        # or
        exclude = ['c', 'd']