Polymarket API in Python: read markets, stream books and place orders

Short answer: Install polymarket-client and use PublicClient. Market data needs no key. Trading needs SecureClient, a wallet and funds. Older guides use py-clob-client, but Polymarket archived it on May 25, 2026, and its README says it no longer works.

We ran the read and stream code below on Nov 5, 2026, with version 0.16.0. We didn't run the order code, because it needs a funded wallet. It follows Polymarket's docs.

The APIs#

The SDK wraps these, and you can also call them directly.

Read a market and its order book#

You'll need Python 3.11 or newer, then pip install polymarket-client.

from polymarket import PublicClient

with PublicClient() as client:
    page = client.list_markets(closed=False, order="volume24hr", ascending=False, page_size=5).first_page()
    market = page.items[0]
    print(market.slug, market.question)

    # the token for this market's Yes side
    yes = market.outcomes.yes
    asset_id = yes.position_id if market.version == "v2" else yes.token_id

    book = client.get_order_book(asset_id=asset_id)
    print("best bid", max(level.price for level in book.bids))
    print("best ask", min(level.price for level in book.asks))
    print("midpoint", client.get_midpoint(asset_id=asset_id))
    print("spread", client.get_spread(asset_id=asset_id))
    print("smallest order", book.min_order_size)

Use max and min for the best prices. When we ran this, book.bids[0] was the lowest bid on the book, at 0.001, and book.asks[0] was the highest ask.

To look up one market, use its slug or its page address: client.get_market(slug="...") or client.get_market(url="...").

Get price history#

points = client.list_price_history(asset_id=asset_id, interval="1d", bucket_seconds=3600).first_page().items
print(points[-1].timestamp, points[-1].price)

Prices come back as Decimal, so convert them before doing floating-point math.

Stream the book#

Streams are async only. The first event is the whole book, and the later ones are changes.

import asyncio

from polymarket import AsyncPublicClient
from polymarket.streams import MarketSpec

async def main(asset_id: str) -> None:
    async with AsyncPublicClient() as client:
        async with await client.subscribe([MarketSpec(asset_ids=[asset_id])]) as stream:
            async for event in stream:
                print(event.topic, event.type)

asyncio.run(main("YOUR_ASSET_ID"))

Place and cancel a limit order#

Trading needs your wallet's private key and address, and pUSD in the account. Keep the key in an environment variable, and never commit it.

import os

from polymarket import SecureClient

with SecureClient.create(
    private_key=os.environ["POLYMARKET_PRIVATE_KEY"],
    wallet=os.environ["POLYMARKET_WALLET_ADDRESS"],
) as client:
    response = client.place_limit_order(asset_id=asset_id, side="BUY", price="0.52", size="10", post_only=True)
    if not response.ok:
        raise RuntimeError(response.message)
    print(response.order_id)
    client.cancel_order(order_id=response.order_id)

post_only=True makes the order rest or get rejected, so it can't take liquidity. Makers pay no fee on Polymarket, while takers pay a fee that depends on the category and price.

What goes wrong#

Test your bot first#

We found no testnet or sandbox in Polymarket's docs, so a bug there costs real money. You can run your quoting logic on Rizon's API first, which takes one call to get a key and uses practice money:

import requests

API = "https://rizon.markets/api/v1"
key = requests.post(f"{API}/accounts").json()["key"]
headers = {"Authorization": f"Bearer {key}"}

print(requests.get(f"{API}/markets").json()["markets"][0]["id"])
print(requests.post(f"{API}/orders", headers=headers, json={"market": "BTC-15s", "side": "up", "size": 10}).json())

It's a different contract. Rizon's book quotes a strike and pays 2×, so you're testing your plumbing and your quoting, not Polymarket's matching. Where to test a trading bot without real money compares the options. If you prefer to work with an AI assistant, see how to build a trading bot with Claude Code.

FAQ#

Does the Polymarket API need an API key?#

Not for market data. Trading and account data need a wallet signature. SecureClient handles the signing and creates the API credentials for you.

What happened to py-clob-client?#

Polymarket archived it on May 25, 2026. py-clob-client-v2 is archived too. The migration guide moves you to polymarket-client.

What are the API's rate limits?#

Polymarket publishes them by endpoint, per IP. For example, /book allows 1,500 requests per 10 seconds, and placing orders allows 5,000 per 10 seconds in a burst. Requests over a limit are delayed rather than rejected.

Is there a Polymarket testnet?#

We found none in its docs. Polymarket has no demo account either.

Can I use the Polymarket API from the US?#

The global platform lists the US as close-only on both the site and the API. Polymarket US is a separate venue, with its own docs.