Pydantic enum field does not get converted to string

You need to use use_enum_values option of model config:

use_enum_values

whether to populate models with the value property of enums, rather than the raw enum. This may be useful if you want to serialise model.dict() later (default: False)

from enum import Enum
from pydantic import BaseModel

class S(str, Enum):
    am='am'
    pm='pm'

class K(BaseModel):
    k:S
    z:str

    class Config:  
        use_enum_values = True  # <--

a = K(k='am', z='rrrr')
print(a.dict())