How to Validate Data in a Python Pipeline

from typing import Any, Iterable


def is_valid_email(email: str) -> bool:
    """Basic email check: one '@', no spaces, dot after '@'."""
    if "@" not in email or " " in email:
        return False
    local, _, domain = email.partition("@")
    return bool(local) and "." in domain


def is_positive_int(value: Any) -> bool:
    """Return True if value is a positive integer (not bool)."""
    if isinstance(value, bool):
        return False
    return isinstance(value, int) and value > 0


def is_non_empty_string_list(values: Iterable[Any]) -> bool:
    """Return True if all items are non-empty strings."""
    return all(isinstance(v, str) and v.strip() for v in values)


def clean_pipeline_record(record: dict) -> dict:
    """Validate common pipeline fields; raise ValueError on bad data."""
    if not is_positive_int(record.get("user_id")):
        raise ValueError(f"Invalid user_id: {record.get('user_id')!r}")
    if not is_valid_email(record.get("email", "")):
        raise ValueError(f"Invalid email: {record.get('email')!r}")
    if not is_non_empty_string_list(record.get("tags", [])):
        raise ValueError(f"Invalid tags: {record.get('tags')!r}")
    return record


if __name__ == "__main__":
    samples = [
        {"user_id": 42, "email": "ada@example.com", "tags": ["python", "data"]},
        {"user_id": -1, "email": "bad@example.com", "tags": ["x"]},
    ]
    for rec in samples:
        try:
            print("OK:", clean_pipeline_record(rec))
        except ValueError as exc:
            print("REJECTED:", exc)