backtrader
Python Backtesting library for trading strategies
...Developers can combine multiple strategies, instruments, and timeframes while resampling or replaying market data. The framework includes a large indicator library, custom indicator support, analyzers, position sizing, commissions, and trading calendars. Its broker simulation supports market, limit, stop, trailing, OCO, and bracket-style orders along with slippage and volume filling. Backtrader can also work with live data and brokerage integrations and provides integrated charting for strategy analysis.