Backtrader

Backtrader is a Python event-driven backtesting framework that processes data bar-by-bar, simulating realistic execution with a built-in broker, order management, and position tracking. Unlike vectorized frameworks (vectorbt, pandas), backtrader walks through history one bar at a time, firing callbacks that let you implement complex order logic that depends on previous fills, partial executions, and conditional brackets.

Event-Driven vs Vectorized

Aspect	Backtrader (event-driven)	vectorbt (vectorized)
Execution model	Bar-by-bar callbacks	Whole-array operations
Speed	Slower (Python loop)	Fast (NumPy/Numba)
Order types	Market, limit, stop, stop-limit, bracket, OCO	Market only (native)
Realism	Built-in broker with commission, slippage, margin	Manual slippage modeling
Multi-timeframe	Native resampledata	Manual alignment
Best for	Complex strategies, bracket orders, portfolio	Fast parameter sweeps, simple signals

Use backtrader when you need:

Bracket orders (entry + stop loss + take profit as a unit)
Stop-limit or trailing stop orders
Order-dependent logic (scale in after first fill, cancel if not filled in N bars)

Related skills