Consider Tradier API, free

Tradier vs Yahoo Finance for Market Scanning

Yahoo Finance (yfinance)

Free, no API key needed	Unofficial/scraping — breaks without warning
Great for EOD price history, fundamentals	No real-time or pre-market quotes
Options chain data available	Rate limits, IP blocks during market hours
Market cap, P/E, earnings dates	Terms of service gray area
Zero cost	Options Greeks often missing/stale

Tradier

Official REST API with real API key	Free tier is paper-trading/delayed only
Real-time quotes (on brokerage account tier)	Needs paid/brokerage tier for live data
Options chains with Greeks (live)
Reliable, won't randomly break
Pre-market / post-market quotes