Point-in-Time Universe Construction

from valuein_sdk import ValueinClient, ValueinError

try:
    with ValueinClient() as client:

        def get_pit_universe(as_of_date: str, index: str = "SP500"):
            """Returns the exact index constituents as of as_of_date."""
            return client.query(f"""
              SELECT r.entity_id, r.symbol, r.name, r.sector
              FROM references r
              JOIN index_membership im ON r.security_id = im.security_id
              WHERE im.index_name = '{index}'
                AND im.start_date <= DATE '{as_of_date}'
                AND (im.end_date IS NULL OR im.end_date > DATE '{as_of_date}')
            """)

        # S&P 500 as of Jan 1, 2020 (before COVID additions)
        universe_2020 = get_pit_universe("2020-01-01")
        print(f"S&P 500 size on 2020-01-01: {len(universe_2020)} companies")

        # Compare to current S&P 500
        universe_now = get_pit_universe("2026-01-01")
        print(f"S&P 500 size on 2026-01-01: {len(universe_now)} companies")

        # Companies that are in today's S&P 500 but weren't in 2020
        new_additions = set(universe_now.symbol) - set(universe_2020.symbol)
        print(f"Added since 2020: {len(new_additions)} companies")
        print(sorted(new_additions)[:10])

except ValueinError as e:
    print(f"Error: {e}")