Create Data Helper Functions in Python for Beginners

import json
from pathlib import Path
from typing import Any, Dict, List


def load_json_file(filepath: str) -> Dict[str, Any]:
    """Load JSON data from a file."""
    with Path(filepath).open("r", encoding="utf-8") as file:
        return json.load(file)


def filter_by_key(
    data: List[Dict[str, Any]], key: str, value: Any
) -> List[Dict[str, Any]]:
    """Return records where data[key] equals value."""
    return [record for record in data if record.get(key) == value]


def sort_by_key(
    data: List[Dict[str, Any]], key: str, reverse: bool = False
) -> List[Dict[str, Any]]:
    """Sort records by a given key."""
    return sorted(data, key=lambda record: record.get(key, 0), reverse=reverse)


def summary_stats(data: List[Dict[str, Any]], key: str) -> Dict[str, float]:
    """Return min, max, and mean of numeric values under key."""
    values = [record[key] for record in data if isinstance(record.get(key), (int, float))]
    if not values:
        return {"min": None, "max": None, "mean": None}
    return {
        "min": min(values),
        "max": max(values),
        "mean": sum(values) / len(values),
    }


def save_json_file(filepath: str, data: Any) -> None:
    """Save data to a JSON file."""
    with Path(filepath).open("w", encoding="utf-8") as file:
        json.dump(data, file, indent=2)


if __name__ == "__main__":
    sample_data = [
        {"name": "Alice", "score": 85},
        {"name": "Bob", "score": 92},
        {"name": "Charlie", "score": 78},
        {"name": "Diana", "score": 92},
    ]

    high_scorers = filter_by_key(sample_data, "score", 92)
    sorted_by_score = sort_by_key(sample_data, "score", reverse=True)
    stats = summary_stats(sample_data, "score")

    print("High scorers (score=92):")
    print(json.dumps(high_scorers, indent=2))

    print("\nSorted by score descending:")
    print(json.dumps(sorted_by_score, indent=2))

    print("\nSummary statistics for score:")
    print(json.dumps(stats, indent=2))