How to Load and Inspect Data Files in Python

from dataclasses import dataclass, field
from pathlib import Path
import json
from typing import Any, Dict, List


@dataclass
class DataLoader:
    """Simple helper to load and inspect data files for beginners."""
    path: Path
    data: Any = field(init=False, default=None)

    def __post_init__(self) -> None:
        self.path = Path(self.path)
        self.load()

    def load(self) -> None:
        """Load JSON or plain text file based on extension."""
        if self.path.suffix == ".json":
            with self.path.open("r", encoding="utf-8") as f:
                self.data = json.load(f)
        else:
            self.data = self.path.read_text(encoding="utf-8")

    def head(self, n: int = 5) -> List[Any]:
        """Return first n records for quick inspection."""
        if isinstance(self.data, list):
            return self.data[:n]
        return list(self.data.items())[:n] if isinstance(self.data, dict) else self.data[:n]

    def info(self) -> Dict[str, Any]:
        """Basic metadata about loaded data."""
        if isinstance(self.data, list):
            return {"type": "list", "length": len(self.data)}
        if isinstance(self.data, dict):
            return {"type": "dict", "keys": list(self.data.keys())}
        return {"type": "text", "characters": len(self.data)}


if __name__ == "__main__":
    # Create a demo JSON file to work with
    sample = Path("sample_people.json")
    sample.write_text('[{"name": "Alice", "age": 30}, {"name": "Bob", "age": 25}]', encoding="utf-8")

    loader = DataLoader(sample)
    print(loader.info())
    print(loader.head(1))

    # Cleanup demo file
    sample.unlink()