import requests


def fetch_idol(idx):
    """Fetch data for a single idol."""
    r = requests.post('https://www.produce101event.com/entry_info.php', data={'idx': idx})
    r.raise_for_status()
    idol_data = r.json()
    if idol_data['result'] == 'success' and idol_data['name']:
        return idol_data
    else:
        return None