Project: resilient study log reader

import json
from pathlib import Path

def total_minutes(path: Path) -> int:
    """Return the sum of valid session minutes in a JSON list."""
    sessions = json.loads(path.read_text(encoding="utf-8"))
    if not isinstance(sessions, list):
        raise ValueError("study log must be a list")
    total = 0
    for session in sessions:
        if not isinstance(session, dict):
            raise ValueError("each session must be an object")
        subject = session.get("subject")
        if not isinstance(subject, str) or not subject.strip():
            raise ValueError("subject must be nonblank text")
        minutes = session.get("minutes")
        if type(minutes) is not int or minutes <= 0:
            raise ValueError("minutes must be a positive integer")
        total += minutes
    return total

try:
    total = total_minutes(Path("study_log.json"))
except FileNotFoundError:
    print("Study log not found")
except UnicodeDecodeError:
    print("Study log is not UTF-8 text")
except json.JSONDecodeError:
    print("Study log is not valid JSON")
except ValueError as error:
    print(f"Invalid study log: {error}")
else:
    print(f"Total study time: {total} min")