Stream JSON Lines records with a generator

import json
from collections.abc import Iterator
from pathlib import Path


def iter_jsonl(path: str | Path) -> Iterator[dict]:
    """Yield one decoded object per non-empty line, with error positions."""
    with open(path, encoding="utf-8") as handle:
        for number, line in enumerate(handle, start=1):
            text = line.strip()
            if not text:
                continue
            try:
                record = json.loads(text)
            except json.JSONDecodeError as exc:
                raise ValueError(f"{path}:{number}: invalid JSON: {exc}") from exc
            if not isinstance(record, dict):
                raise ValueError(f"{path}:{number}: expected a JSON object")
            yield record


def write_jsonl(path: str | Path, records: list[dict]) -> None:
    """Append records in JSON Lines format, one object per line."""
    with open(path, "a", encoding="utf-8") as handle:
        for record in records:
            handle.write(json.dumps(record, ensure_ascii=False) + "\n")


if __name__ == "__main__":
    write_jsonl("events.jsonl", [{"id": 1}, {"id": 2}])
    print(list(iter_jsonl("events.jsonl")))