a.py

# current code.  BAD.
import uuid
from uuid import UUID
from typing import cast
from dataclasses import dataclass

@dataclass
class DC:
    uuid: UUID


print(type(DC(42).uuid)) #=> int!
print(type(DC('42').uuid)) #=> str!
print(type(DC('954df9cd-5539-4552-975c-d42223731620').uuid)) #=> str!
print(type(DC(cast(UUID, '954df9cd-5539-4552-975c-d42223731620')).uuid)) #=> omfg str!
print(type(DC(cast(UUID, ['what', 'the', 'eff'])).uuid)) #=> list

dc = DC(uuid.uuid4())

dc.anything_goes = True # not even a warning...

some_form = {'name':'value'}
dc.silent_error = some_form['name'] # remembering that our forms have ZERO type checking, this one is __very easy to make

b.py

# new code.  GOOD.
from uuid import UUID
from typing import cast

from pydantic import BaseModel

class DC(BaseModel):
    uuid: UUID

try:
    print(type(DC(uuid=42).uuid))
except Exception as e:
    print(e)
    """
		1 validation error for DC
		uuid
		  UUID input should be a string, bytes or UUID object [type=uuid_type, input_value=42, input_type=int]
			For further information visit https://errors.pydantic.dev/2.4/v/uuid_type
    """

print(type(DC(uuid=UUID('954df9cd-5539-4552-975c-d42223731620')).uuid)) #=> UUID! obvi
print(type(DC(uuid=str('954df9cd-5539-4552-975c-d42223731620')).uuid)) #=> UUID!  i'm cry ;-)

try:
    dc = DC(uuid='954df9cd-5539-4552-975c-d42223731620')
    dc.some_form_field_error = 'whoops!'
except Exception as e:
    print(e)
    """
		"DC" object has no field "some_form_field_error"
    """