Observers

Observers track and visualize trading activity.

Observers Module - Strategy monitoring observers.

This module provides observers for monitoring and recording strategy execution. Observers track metrics like cash, value, drawdown, trades, and benchmark data during backtesting.

Available Observers:

  • Benchmark: Benchmark data (price) for comparison

  • Broker: Cash and value tracking

  • BuySell: Buy/sell signal visualization

  • DrawDown: Drawdown tracking and visualization

  • LogReturns: Log returns tracking

  • TimeReturn: Returns by time period

  • Trades: Trade tracking

  • TradeLogger: Comprehensive logging (orders, trades, positions, indicators, signals)

Example

Adding observers to a strategy: >>> cerebro.addobserver(bt.observers.DrawDown) >>> cerebro.addobserver(bt.observers.Trades) >>> cerebro.addobserver(bt.observers.TradeLogger, log_dir=’./logs’)

Overview

Observers are special indicators that track the state of the trading system. They are used for visualization and do not affect trading logic.

Built-in Observers

  • Broker: Cash and portfolio value

  • BuySell: Buy/sell markers on chart

  • Trades: Trade markers and P&L

  • DrawDown: Drawdown visualization

  • TimeReturn: Period returns

  • Benchmark: Compare against benchmark

Using Observers

cerebro = bt.Cerebro(stdstats=False)  # Disable default observers

# Add specific observers
cerebro.addobserver(bt.observers.Broker)
cerebro.addobserver(bt.observers.BuySell)
cerebro.addobserver(bt.observers.Trades)
cerebro.addobserver(bt.observers.DrawDown)

# Run and plot
cerebro.run()
cerebro.plot()

Benchmark Observer

# Add benchmark data
benchmark = bt.feeds.YahooFinanceCSVData(dataname='SPY.csv')
cerebro.adddata(benchmark, name='benchmark')

# Add benchmark observer
cerebro.addobserver(
    bt.observers.Benchmark,
    data=benchmark,
    timeframe=bt.TimeFrame.NoTimeFrame
)

Creating Custom Observers

class MyObserver(bt.Observer):
    lines = ('custom',)
    plotinfo = dict(plot=True, subplot=True)

    def next(self):
        # Track custom metric
        self.lines.custom[0] = self._owner.broker.getvalue()