How to Parse Data in Python: A Beginner's Helper

import json
from datetime import datetime
from typing import Dict, List


def parse_data(payload: str) -> Dict[str, List]:
    """Parse a JSON payload and extract useful fields."""
    raw = json.loads(payload)
    users = raw.get("users", [])

    parsed = {
        "names": [],
        "emails": [],
        "signup_dates": [],
    }

    for user in users:
        parsed["names"].append(user.get("name", "unknown"))
        parsed["emails"].append(user.get("email", "no-email"))
        date_str = user.get("signup_date", "1970-01-01")
        parsed["signup_dates"].append(datetime.fromisoformat(date_str))

    return parsed


def summarize_parsed(data: Dict[str, List]) -> str:
    """Generate a short summary of the parsed results."""
    count = len(data["names"])
    newest = max(data["signup_dates"]).date().isoformat()
    return f"Parsed {count} users; newest signup on {newest}."


if __name__ == "__main__":
    sample_payload = json.dumps({
        "users": [
            {"name": "Ana", "email": "ana@example.com", "signup_date": "2023-05-01"},
            {"name": "Bob", "email": "bob@example.com", "signup_date": "2024-02-14"},
        ]
    })

    result = parse_data(sample_payload)
    print(summarize_parsed(result))