How Do I Build a Polymarket Trading Bot in Python? The 2026 Guide

A Polymarket trading bot is four loops: discover markets (Gamma API), generate signals (your strategy over prices and data), execute (py-clob-client-v2 against the CLOB), and manage risk (positions, rate limits, failures). Since the April 28, 2026 hard cutover, the official Python SDK is py-clob-client-v2 — the V1 package and V1-signed orders stopped working on production, so every pre-2026 tutorial snippet needs that migration first.

What does the 2026 stack look like?

The V2 SDK wraps the REST API into Python methods: initialize once with your credentials, reuse the client object for every call, and it handles request signing via your private key automatically.

What is the minimal working skeleton?

A minimal bot is a ClobClient with wallet key, chain_id 137, signature_type 1 and the proxy funder, wrapped in a loop that polls or subscribes, decides, and places signed orders.

from py_clob_client_v2.client import ClobClient

# L2 auth: API key derived from your wallet signature
client = ClobClient(
    "https://clob.polymarket.com",
    key=PRIVATE_KEY,        # your Polygon wallet key
    chain_id=137,           # Polygon mainnet
    signature_type=1,       # proxy wallet (Polymarket default)
    funder=PROXY_ADDRESS,   # your Polymarket proxy wallet
)

# 1. Discover: pull an active market
market = client.get_market(condition_id)

# 2. Price: read the current book
book = client.get_order_book(token_id)

# 3. Signal: your logic (here: naive midpoint fair value)
fair = estimate_fair_probability(market, book)
mid = (book.best_bid + book.best_ask) / 2

# 4. Execute: only trade when your edge clears fees + spread
if fair - mid > edge_threshold:
    client.create_order(
        MarketOrderArgs(
            token_id=book.token_id,
            amount=10,              # USDC size
            side="BUY",
        )
    )

That skeleton is honest about one thing: the infrastructure is the easy half. The edge is the hard half — a bot without a positive-expectancy signal is a fee-paying random-trade generator.

What do you need before the first order?

1. Wallet + proxy — Polymarket routes trading through a proxy wallet; the proxy address is your funder parameter
2. API credentials — derived from a wallet signature (L2 auth); never ship your private key to any service that doesn’t need it
3. pUSD collateral — on Polygon, in the account the bot trades
4. Rate-limit budget — per-signer token buckets; a loop that polls harder than its tier gets 429s (see the rate-limits guide on this hub)

What should the risk loop check?

• Position caps — per market and per category; no single-event blowups
• Fee-adjusted edge — taker fees up to $1.75 per 100 shares (crypto) plus the spread must sit inside your expected value
• Failure handling — 429 → honor Retry-After; 400 → log payload, don’t retry blind; timeout → reconcile positions before re-entering
• Clock skew — signed requests need fresh timestamps; sync against GET /v1/info/time
• Kill switch — one flag that cancels all orders and flattens; test it before you need it

What broke in the V2 migration (and how to fix)?

FAQ

Q: What language and library for a Polymarket bot in 2026? A: Python with py-clob-client-v2 — the official SDK after the April 28, 2026 cutover. The older py-clob-client package is dead on production.

Q: Do I need my private key in the bot? A: The signing key must exist where the bot runs, but the safest pattern is a proxy wallet: your main key stays cold, the proxy key signs trade requests. For purely read-only loops (prices, books), no key is needed at all.

Q: How much capital to start a bot? A: Enough to make fees and spread mathematically survivable: single-digit USDC per trade, $50-100 total, is plenty to validate plumbing. Edge, not capital, decides viability.

Q: Can a bot get rate-limited? A: Yes — order placement is token-bucketed per signer (Standard tier: 40 orders/s burst 60) and IP-throttled globally. Design loops to respect Retry-After.

Q: Where do I get historical data for backtesting? A: The Data API v2 (/v2/prices-history, /v2/trades) plus on-chain Polygon records for deep history.

Sources

• docs.polymarket.com — CLOB API
• AgentBets — py-clob-client-v2 reference

Disclaimer

Not financial advice. Educational purposes only. Updated October 2026.