yfinance-options

yfinance Options Data

Pull options data via the yfinance Python library. Returns structured chains for downstream skills (iv-surface, vol-skew, options-payoff).

---

Step 1: Check Tool Availability

!`python3 -c "import yfinance, sys; print(f'yfinance {yfinance.__version__} OK')" 2>&1 | head -3`

If yfinance is not installed: pip install yfinance. Do NOT proceed silently — surface the missing dependency.

---

Step 2: Resolve User Intent

Intent	Method	Params
List all expiries	Ticker.options	ticker
Single expiry chain	Ticker.option_chain(expiry)	ticker, expiry (YYYY-MM-DD)
All expiries chain	loop over options	ticker
Spot price	Ticker.fast_info['lastPrice']	ticker
Historical underlying	Ticker.history(...)	ticker, period
Dividends	Ticker.dividends	ticker

For "0DTE chain" → today's date if listed (SPX/SPY/QQQ have daily expiries). If today not listed, return the next trading day.

For "weeklies" → all Fridays in the next 4 weeks.

For "monthlies" → 3rd-Friday expiries only (filter with a calendar check).

---

Step 3: Code Template

See references/api_reference.md for the full template. Skeleton:

import yfinance as yf
import pandas as pd

def get_chain(ticker, expiry=None):
    t = yf.Ticker(ticker)
    spot = t.fast_info['lastPrice']
    if expiry is None:
        expiry = t.options[0]  # nearest
    chain = t.option_chain(expiry)
    calls = chain.calls.copy()
    puts = chain.puts.copy()
    calls['type'] = 'call'
    puts['type'] = 'put'
    df = pd.concat([calls, puts], ignore_index=True)
    df['mid'] = (df['bid'] + df['ask']) / 2
    df['spread'] = df['ask'] - df['bid']
    df['spread_pct'] = df['spread'] / df['mid'].replace(0, float('nan'))
    return {'spot': spot, 'expiry': expiry, 'chain': df}

---

Step 4: Quality Filters (apply BEFORE returning data)

Filter	Reason
Drop bid = 0 or ask = 0	Stale, no market
Drop spread_pct > 0.5	Illiquid
Drop volume = 0 AND OI < 10	No interest
Drop mid < $0.05	Rounding noise

If after filtering > 80% of the chain is gone, report that the chain is illiquid — don't pretend a clean chain exists.

---

Step 5: Known Limitations (be explicit)

• yfinance IV is sometimes stale (cached) or zero. Re-compute IV downstream via Newton-Raphson if you need accuracy.
• No Greeks in raw chain. Use greeks-calculator after pricing.
• Quotes delayed ≥ 15 min for most users; not for real-time trading.
• No European-style index detection: SPX is European, but yfinance does not flag it. Use the american flag manually when relevant.
• Adjusted closes for splits: historical chain data can have stale strikes after a split. Verify with Ticker.actions.

If the user needs real-time, recommend a paid feed (Polygon, IEX, ORATS).

---

Step 6: Respond / Hand Off

Return the structured chain plus:

1. Spot price and timestamp.
2. Expiry chosen and how many strikes survive filtering.
3. A 5-row preview (ATM ± 2 strikes, both call and put) so the user sees what's there.
4. Suggested next skill: iv-surface for fitting, vol-skew for skew metrics, options-payoff for trade visualization.

---

Reference Files

• references/api_reference.md — Full template with batch expiry pulling, IV recomputation, and rate-limit handling