
backtrader
Event-driven backtesting with bar-by-bar execution, complex order types, multiple analyzers, and custom indicators
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/agiprolabs/claude-trading-skills --skill backtrader- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads backtrader automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
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)
- Multi-timeframe strategies (daily signals, hourly execution)
- Realistic commission and slippage modeling
Use vectorbt when you need:
- Fast parameter optimization over thousands of combinations
- Simple long/short signals without complex order management
- Quick prototyping and statistical analysis of results
Core Concepts
Backtrader has five core objects that interact through an event loop:
1. Cerebro (the engine)
The central orchestrator. You add strategies, data feeds, analyzers, and sizers to Cerebro, then call run().
import backtrader as bt
cerebro = bt.Cerebro()
cerebro.addstrategy(MyStrategy, fast_period=10, slow_period=30)
cerebro.adddata(data_feed)
cerebro.broker.setcash(100_000)
cerebro.broker.setcommission(commission=0.003) # 0.3%
cerebro.addanalyzer(bt.analyzers.SharpeRatio, _name="sharpe")
cerebro.addanalyzer(bt.analyzers.DrawDown, _name="drawdown")
cerebro.run()
2. Strategy (your logic)
A Strategy subclass contains all trading logic. Key methods:
__init__()— Define indicators. Runs once before backtesting starts.next()— Called on every bar. Place orders here.notify_order(order)— Called when order status changes (submitted, accepted, completed, canceled, margin, expired).notify_trade(trade)— Called when a trade opens or closes. Access P&L here.
class EMACrossover(bt.Strategy):
params = (
("fast_period", 10),
("slow_period", 30),
)
def __init__(self) -> None:
self.ema_fast = bt.ind.EMA(period=self.p.fast_period)
self.ema_slow = bt.ind.EMA(period=self.p.slow_period)
self.crossover = bt.ind.CrossOver(self.ema_fast, self.ema_slow)
def next(self) -> None:
if not self.position:
if self.crossover > 0:
self.buy()
elif self.crossover < 0:
self.close()
3. Data Feed
Backtrader data feeds provide OHLCV lines. The most common approach is loading from a pandas DataFrame:
import pandas as pd
df = pd.DataFrame({
"open": [...], "high": [...], "low": [...],
"close": [...], "volume": [...],
}, index=pd.DatetimeIndex([...]))
data = bt.feeds.PandasData(dataname=df)
cerebro.adddata(data)
For CSV files:
data = bt.feeds.GenericCSVData(
dataname="ohlcv.csv",
dtformat="%Y-%m-%d",
openinterest=-1, # no open interest column
)
4. Broker
The built-in broker simulates order execution with configurable cash, commission, and slippage.
cerebro.broker.setcash(100_000)
cerebro.broker.setcommission(commission=0.003) # 0.3% per trade
# Cheat-on-open: execute at the open of the signal bar (avoids lookahead)
cerebro.broker.set_coo(True)
5. Analyzers
Analyzers compute performance metrics after the backtest completes.
cerebro.addanalyzer(bt.analyzers.SharpeRatio, _name="sharpe",
riskfreerate=0.0, annualize=True, timeframe=bt.TimeFrame.Days)
cerebro.addanalyzer(bt.analyzers.DrawDown, _name="drawdown")
cerebro.addanalyzer(bt.analyzers.TradeAnalyzer, _name="trades")
cerebro.addanalyzer(bt.analyzers.Returns, _name="returns")
results = cerebro.run()
strat = results[0]
sharpe = strat.analyzers.sharpe.get_analysis()
dd = strat.analyzers.drawdown.get_analysis()
trades = strat.analyzers.trades.get_analysis()
Order Types
Backtrader supports complex order types critical for realistic crypto backtesting.
Market Order
self.buy() # market buy
self.sell() # market sell
self.close() # close current position
Limit Order
self.buy(exectype=bt.Order.Limit, price=95.0)
self.sell(exectype=bt.Order.Limit, price=105.0)
Stop Order
Triggers a market order when price reaches the stop level:
self.sell(exectype=bt.Order.Stop, price=90.0) # stop loss
Stop-Limit Order
Triggers a limit order when price reaches the stop level:
self.buy(exectype=bt.Order.StopLimit, price=100.0, plimit=101.0)
Bracket Order
Entry + stop loss + take profit as an atomic unit. If the stop fills, the take profit is canceled (and vice versa).
self.buy_bracket(
price=100.0, # entry limit
stopprice=95.0, # stop loss
limitprice=110.0, # take profit
exectype=bt.Order.Limit,
stopexec=bt.Order.Stop,
limitexec=bt.Order.Limit,
)
See references/strategy_patterns.md for bracket order patterns with ATR-based stops.
Position Sizing (Sizers)
Sizers determine how many units to buy/sell per order.
# Fixed size
cerebro.addsizer(bt.sizers.FixedSize, stake=100)
# Percent of portfolio
cerebro.addsizer(bt.sizers.PercentSizer, percents=95)
# All available cash
cerebro.addsizer(bt.sizers.AllInSizer, percents=95)
Custom sizer:
class RiskSizer(bt.Sizer):
params = (("risk_pct", 0.02),)
def _getsizing(self, comminfo, cash, data, isbuy):
risk_amount = cash * self.p.risk_pct
atr = self.strategy.atr[0]
if atr <= 0:
return 0
size = risk_amount / atr
return int(size)
Crypto Considerations
24/7 Markets
Crypto trades around the clock. When using daily bars, there are no weekends to skip. Set the session times or use sessionstart/sessionend if analyzing specific windows.
High Fees
DEX swaps on Solana typically cost 0.25-0.30% per trade. Set commission accordingly:
cerebro.broker.setcommission(commission=0.003) # 0.3% round trip per side
Fractional Sizing
Crypto allows fractional units. Backtrader supports this natively -- no special config needed.
Slippage
For realistic simulation, enable cheat-on-open and add slippage:
cerebro.broker.set_coo(True)
cerebro.broker.set_slippage_perc(0.001) # 0.1% slippage
Volatile Data
Crypto OHLCV data often has extreme wicks. Use ATR-based stops rather than fixed percentage stops to adapt to volatility.
Multi-Timeframe
Backtrader can resample data to multiple timeframes within a single strategy:
data_1h = bt.feeds.PandasData(dataname=df_1h)
cerebro.adddata(data_1h)
# Resample 1h to daily
cerebro.resampledata(data_1h, timeframe=bt.TimeFrame.Days, compression=1)
Access in strategy:
def __init__(self):
self.ema_1h = bt.ind.EMA(self.datas[0], period=20) # hourly
self.ema_daily = bt.ind.EMA(self.datas[1], period=20) # daily
Custom Indicators
class SpreadIndicator(bt.Indicator):
lines = ("spread", "zscore",)
params = (("period", 20),)
def __init__(self):
mean = bt.ind.SMA(self.data, period=self.p.period)
std = bt.ind.StdDev(self.data, period=self.p.period)
self.lines.spread = self.data - mean
self.lines.zscore = self.lines.spread / std
Plotting
Backtrader includes matplotlib-based plotting:
cerebro.plot(style="candlestick", volume=True)
For headless environments, save to file:
import matplotlib
matplotlib.use("Agg")
figs = cerebro.plot(style="candlestick")
figs[0][0].savefig("backtest_result.png", dpi=150)
Integration with Other Skills
- pandas-ta: Compute indicators externally, add as data feed columns. See
references/api_guide.mdfor adding extra lines. - trading-visualization: Export trade log from
notify_tradeand plot with the visualization skill. - position-sizing: Use the
position-sizingskill for Kelly or volatility-targeting sizers. - risk-management: Apply portfolio-level guardrails from the
risk-managementskill as strategy filters. - slippage-modeling: Use slippage estimates from the
slippage-modelingskill to configureset_slippage_perc.
Files
References
references/api_guide.md— Cerebro, Strategy, Broker, Analyzer, Data Feed API referencereferences/strategy_patterns.md— Reusable strategy patterns: crossover, mean reversion, multi-timeframe, custom indicators
Scripts
scripts/backtest_strategy.py— Complete EMA crossover backtest with analyzers and synthetic datascripts/bracket_orders.py— Bracket order demonstration with RSI entry and ATR-based stops
Quick Start
uv pip install backtrader pandas numpy matplotlib
python scripts/backtest_strategy.py --demo
python scripts/bracket_orders.py --demo
FAQ
What does the backtrader skill do?
Event-driven backtesting with bar-by-bar execution, complex order types, multiple analyzers, and custom indicators
How do I install backtrader?
Run npx skills add https://github.com/agiprolabs/claude-trading-skills --skill backtrader in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/backtrader/ (personal) or .claude/skills/backtrader/ (project).
Which AI agents can use backtrader?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is backtrader safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains backtrader?
It is published by agiprolabs in agiprolabs/claude-trading-skills. It has 504 recorded installs.
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