Initialize a Literal enum in a pydantic model

Question

pydantic supports regular enums just fine, and one can initialize an enum-typed field using both an enum instance and an enum value:

from enum import Enum
from pydantic import BaseModel

class MyEnum(Enum):
    FOO = 'foo'
    BAR = 'bar'

class MyModel(BaseModel):
    x: MyEnum

MyModel(x=MyEnum.BAR)  # Enum instance, works
MyModel(x='foo')       # Enum value, works
MyModel(x='?')         # Fails, as expected

pydantic also supports typing.Literal:

from typing import Literal
from pydantic import BaseModel

class MyModel(BaseModel):
    x: Literal['foo']

MyModel(x='foo')  # Works
MyModel(x='bar')  # Fails, as expected

Now I want to combine enums and literals, i.e. force a field value to equal one particular enum instance. However, I still want to be able to pass the correct enum value (i.e. not only the correct enum instance), and that doesn't seem to work:

from enum import Enum
from typing import Literal
from pydantic import BaseModel

class MyEnum(Enum):
    FOO = 'foo'
    BAR = 'bar'

class MyModel(BaseModel):
    x: Literal[MyEnum.FOO]

MyModel(x=MyEnum.FOO)  # Enum instance, works
MyModel(x=MyEnum.BAR)  # Fails, as expected
MyModel(x='foo')       # Enum value, fails but I'd like it to work

Answer 1

Try to use string based Enum. Like so:

from enum import Enum
from typing import Literal
from pydantic import BaseModel


class MyEnum(str, Enum):
    FOO = 'foo'
    BAR = 'bar'


class MyModel(BaseModel):
    x: Literal[MyEnum.FOO]


MyModel(x=MyEnum.FOO)  # Enum instance, works
# MyModel(x=MyEnum.BAR)  # Fails, as expected
MyModel(x='foo')       # String value, works