Bollinger Bands (ta.bbands)

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Construct upper and lower bands around a moving average using standard deviation, providing bandwidth and relative position.

Indicator catalog · How to use indicators

Run this example

This complete script uses bundled data. It observes the selected output without placing trades.

import numpy as np
from openbacktesting import Backtest, Strategy
from openbacktesting.test import GOOG

data = GOOG.copy()

class Example(Strategy):
    def init(self):
        self.value = self.ta.bbands(self.close)
        self.latest_value = None

    def next(self):
        channel = self.value.lower
        if channel.valid[-1]:
            self.latest_value = float(channel[-1])

result = Backtest(data, Example).run()
print(result["_strategy"].latest_value)

Call and parameters

self.ta.bbands(
    source=None,
    *,
    length=5,
    std=2.0,
    ddof=0,
    mamode='sma',
    inputs=None,
    backend=None,
    required_outputs=None,
)

Register in init(). Read the returned channel in next() after checking valid[-1].

Parameter	Meaning	Type	Default	Allowed values
length	Calculation window in observations.	int	5	Minimum: 2
std	Standard-deviation multiplier.	float	2.0	Minimum: 1e-08
ddof	Degrees of freedom subtracted from the variance denominator.	int	0	Minimum: 0
mamode	Moving-average algorithm; choose one of the listed values.	str	sma	Allowed values: ['sma', 'ema', 'rma', 'wma']

source/named source arguments accept a column name or same-run single-channel handle. Alternatively, inputs maps each input below to a column or handle. backend selects a supported implementation; required_outputs selects channels for readiness diagnostics. See shared arguments and handles.

Inputs and outputs

Required inputs: close.

Channel	Meaning
lower	Lower band
middle	Middle line
upper	Upper band
bandwidth	Band width relative to the middle line
percent	Position between the lower and upper bands (fraction)

Reading values safely

Insufficient history or missing inputs can make a channel invalid. Check that channel's valid mask; ready is diagnostic and never suppresses next(). Multi-output results may have different valid channels on the same bar.

Indicator catalog · Custom calculations