bespoke

A Python library for backtesting, comparing, and building trading strategies. Bespoke provides a clean API for defining strategy logic, running historical simulations with realistic slippage modeling, and evaluating performance through standard financial metrics like Sharpe ratio, CAGR, max drawdown, and rolling-window composite scores.

Install

pip install bespoke

Quick Start

from bespoke import Backtester
from bespoke.strategies import get_strategy

strategy = get_strategy("spy_buy_and_hold")
bt = Backtester(strategy, start="2020-01-01", end="2025-12-31")
result = bt.run()
print(f"Return: {result['metrics']['total_return']:.2%}")
print(f"Sharpe: {result['metrics']['sharpe_ratio']:.2f}")

CLI

Bespoke includes a command-line interface for quick analysis.

# List all available strategies
bespoke list

# Show details for a strategy
bespoke info spy_buy_and_hold

# Run a backtest
bespoke backtest spy_buy_and_hold --start 2020-01-01 --end 2025-12-31

# Run on all 28 rolling windows (1Y-15Y x 4 end years)
bespoke backtest spy_buy_and_hold --windows

# Compare two strategies side by side
bespoke compare spy_buy_and_hold balanced_sixty_forty

# Save results to JSON
bespoke save spy_buy_and_hold --output results.json

Creating a Custom Strategy

Subclass BaseStrategy and implement generate_signals:

from bespoke.strategies.base import BaseStrategy, StrategyConfig

class MomentumStrategy(BaseStrategy):
    def __init__(self):
        super().__init__(StrategyConfig(
            name="momentum",
            description="Buy assets with positive 50-day momentum",
            universe=["SPY", "QQQ", "IWM"],
            rebalance_frequency="monthly",
            max_position_size=0.50,
        ))

    def generate_signals(self, date, prices, portfolio, data):
        signals = {}
        for sym in self.universe:
            if sym in data and date in data[sym].index:
                sma50 = data[sym].loc[:date, "SMA_50"].iloc[-1]
                if prices.get(sym, 0) > sma50:
                    signals[sym] = 1.0
        return signals

Then backtest it:

from bespoke import Backtester

bt = Backtester(MomentumStrategy(), start="2020-01-01")
result = bt.run()

Architecture

bespoke/
  core/
    backtester.py    Event-driven backtester with slippage + rebalancing
    portfolio.py     Position tracking, cash management, trade history
    metrics.py       Sharpe, Sortino, CAGR, drawdown, alpha/beta, composite
  data/
    fetcher.py       OHLCV via yfinance with parquet caching + indicators
  strategies/
    base.py          BaseStrategy + StrategyConfig dataclass
    registry.py      Auto-discovery and name-based lookup
    generic/         Baseline strategies (SPY, 60/40, three-fund)
  compat/
    loader.py        Bridge to load external strategy collections
  cli/
    main.py          Command-line interface (argparse)

Data flow:

1. Backtester loads OHLCV data via fetch_ohlcv (cached locally)
2. Technical indicators are added (SMA, RSI, MACD, Bollinger, ATR)
3. On each trading day, Strategy.generate_signals() returns target weights
4. Portfolio executes rebalancing trades with slippage
5. compute_metrics() evaluates the resulting equity curve

Available Strategies

Three baseline strategies are included out of the box:

These baselines serve as the performance bar that any custom strategy must clear to justify its complexity.

The bespoke.compat module provides a bridge to load additional strategy collections. See bespoke/compat/loader.py for details.

Metrics

Every backtest produces:

• Total Return and CAGR -- absolute and annualized performance
• Sharpe Ratio -- risk-adjusted return (excess over risk-free rate)
• Sortino Ratio -- penalizes only downside volatility
• Max Drawdown -- worst peak-to-trough decline
• Calmar Ratio -- CAGR / max drawdown
• Win Rate -- fraction of positive trading days
• Alpha / Beta -- vs benchmark (when benchmark data available)
• Composite Score -- rolling-window consistency metric

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/my-strategy)
3. Add your strategy in src/bespoke/strategies/
4. Write tests in tests/
5. Run pytest to verify
6. Submit a pull request

License

MIT License. See LICENSE for details.