Arbitrage Calculator Example - Python

Find cross-bookmaker margins by identifying odds discrepancies across every Australian book.

What you'll build

A script that:

Scans all bookmakers for odds discrepancies
Calculates arbitrage opportunities on two-sided markets
Shows optimal stake sizing
Calculates guaranteed profit percentage

Perfect for: Finding cross-book margins, comparing bookmaker odds, beating the vig

Prerequisites

Python 3.8+
SockOdds API key (free)
Basic Python

Complete code

Step 1: Setup project

mkdir arb-finder && cd arb-finder
python -m venv venv && source venv/bin/activate
pip install requests

Step 2: Create arb_calculator.py

# arb_calculator.py
import os, sys, requests

API_KEY = os.environ["SOCKODDS_KEY"]
BASE = "https://api.sockodds.com/v2"
LEAGUE = sys.argv[1] if len(sys.argv) > 1 else "AFL"
MIN_MARGIN = 0.5          # percent

def fetch_events(league):
    events, cursor = [], None
    while True:
        params = {"leagueID": league, "oddsAvailable": "true", "limit": 100, **({"cursor": cursor} if cursor else {})}
        r = requests.get(f"{BASE}/events", params=params, headers={"x-api-key": API_KEY}); r.raise_for_status()
        body = r.json(); events += body["data"]; cursor = body.get("nextCursor")
        if not cursor: break
    return events

def best_price(odd):
    """Best available decimal across books, and which book."""
    best = (None, None)
    for book, q in odd["byBookmaker"].items():
        if q.get("available") and q.get("decimal") and (best[0] is None or q["decimal"] > best[0]):
            best = (q["decimal"], book)
    return best

def find_arbs(event):
    odds = event["odds"]; seen = set(); out = []
    for odd_id, odd in odds.items():
        opp = odd.get("opposingOddID")
        if not opp or opp not in odds or odd_id in seen: continue
        seen.update({odd_id, opp})
        # a two-sided market only arbs when both sides are on the same line
        a_line, b_line = odd.get("bookOverUnder") or odd.get("bookSpread"), odds[opp].get("bookOverUnder") or odds[opp].get("bookSpread")
        (pa, ba), (pb, bb) = best_price(odd), best_price(odds[opp])
        if not pa or not pb: continue
        total = 1 / pa + 1 / pb
        if total < 1:
            margin = (1 / total - 1) * 100
            stake_a, stake_b = (1 / pa) / total, (1 / pb) / total
            out.append(dict(market=odd["marketName"], side_a=(ba, pa, stake_a), side_b=(bb, pb, stake_b), margin=margin, lines=(a_line, b_line)))
    return out

if __name__ == "__main__":
    events = fetch_events(LEAGUE)
    print(f"scanned {len(events)} {LEAGUE} events")
    for e in events:
        if e["info"].get("stale"): continue
        for arb in find_arbs(e):
            if arb["margin"] < MIN_MARGIN: continue
            (ba, pa, sa), (bb, pb, sb) = arb["side_a"], arb["side_b"]
            print(f"\n{e['eventID']}  {arb['market']}  margin {arb['margin']:.2f}%")
            print(f"  {ba:12} @ {pa:.2f}  stake {sa*100:5.1f}%   {e['links']['bookmakers'].get(ba, '')}")
            print(f"  {bb:12} @ {pb:.2f}  stake {sb*100:5.1f}%   {e['links']['bookmakers'].get(bb, '')}")

Step 3: Run it

SOCKODDS_KEY=so_live_… python arb_calculator.py AFL

Expected output

scanned 6 AFL events

afl_2026-09-05_collingwood_vs_geelong  Total Points  margin 1.23%
  sportsbet    @ 2.05  stake 49.4%   https://www.sportsbet.com.au/…
  betfairexchange @ 2.00  stake 50.6%   https://www.betfair.com.au/…

How it works

1. Fetch events with odds

Paged with cursor; every market and every book arrives in one object.

2. Use decimal directly

No American-to-decimal conversion — every book entry carries decimal.

3. Pair the sides

opposingOddID names the other side; each pair is scanned once.

4. Find the best price per side

Skip available: false.

5. Calculate arbitrage

Total implied probability below 1 → margin 1/total − 1.

6. Calculate optimal stakes

Proportional to (1/price)/total.

Enhancements

Minimum profit filter

MIN_MARGIN = 1.0

Middles

# with includeAltLines=true, compare line values across books for each side:
# Home -5.5 at book A and Away +6.5 at book B is a middle on a 6-point margin

Real-time monitoring

import time
while True:
    ...scan...
    time.sleep(150)

Troubleshooting

"No arbitrage opportunities found"

Normal most of the time. Lower MIN_MARGIN to see near-misses, or add includeAltLines=true.

Negative profit calculation

Both sides must be on the same line — the script prints the lines so you can check.