The functions signatures already show the difference between these 2 approaches

comparing_parsing_to_validation.py

from dataclasses import dataclass
from typing import List

# Users have:
# a name which is a non-empty string
# an age which is a positive int
# at least one hobbie (which is a non empty list)


@dataclass
class User:
    name: str
    age: int
    hobbies: List[str]


def validate_user(possible_user: dict) -> None:
    """Validates the inputs and raises a ValueError if unsuccessful"""


def parse_user(possible_user: dict) -> User:
    """Parses the input and returns a User if successful"""