CCXT Hyperliquid historical candles

import os
import ccxt

ex = ccxt.hyperliquid()
ex.load_markets()                     # markets come from Hyperliquid's own API
ex.urls["api"]["public"] = f"https://api.ironflow.sh/rpc/{os.environ['IRONFLOW_KEY']}"
ex.rateLimit = 250                    # one candle call a second fits a free key


def history(symbol, timeframe, days):
    """Up to `days` of candles, older than now, oldest first."""
    step = ex.parse_timeframe(timeframe) * 1000
    end = ex.milliseconds() // step * step
    stop = end - days * 86_400_000
    candles = {}
    while end > stop:
        since = max(stop, end - 1000 * step)
        page = ex.fetch_ohlcv(symbol, timeframe, since=since, params={"until": end})
        if not page:
            break
        candles.update({c[0]: c for c in page})
        end = page[0][0]
    return [candles[t] for t in sorted(candles)]


rows = history("BTC/USDC:USDC", "1m", days=7)
print(len(rows), rows[0], rows[-1])