Bollinger Bands (BB)

Warmup Window

Minimum bars needed: period bars (default params: 20 bars (period=20))

Both the SMA middle line and the standard deviation need period bars of data. After warmup, all three bands update in real-time.

✅ After the warmup window is filled, this indicator produces a new value on every incoming bar in real-time.

Lagging Indicator

The bands and middle line lag behind both price and volatility changes.

Event	Lag	Detail
Middle band (SMA) reacts to price reversal	≈ `period / 2` bars	SMA has lag ≈ period/2
Bands widen/narrow after volatility change	≈ `period / 2` bars	Std dev computed over same rolling window
Price touches upper/lower band	≈ `period / 2` bars	Bands trail the actual volatility shift

Formula for custom params: lag ≈ period / 2

Bollinger Bands are a volatility indicator that consists of a middle band (SMA) and two outer bands (standard deviations). They help traders identify overbought and oversold conditions.

def bollinger_bands(
    data: Union[PdDataFrame, PlDataFrame],
    source_column='Close',
    period=20,
    std_dev=2,
    middle_band_column_result_column='bollinger_middle',
    upper_band_column_result_column='bollinger_upper',
    lower_band_column_result_column='bollinger_lower'
) -> Union[PdDataFrame, PlDataFrame]:

Example

from investing_algorithm_framework import download

from pyindicators import bollinger_bands

pl_df = download(
    symbol="btc/eur",
    market="binance",
    time_frame="1d",
    start_date="2023-12-01",
    end_date="2023-12-25",
    save=True,
    storage_path="./data"
)
pd_df = download(
    symbol="btc/eur",
    market="binance",
    time_frame="1d",
    start_date="2023-12-01",
    end_date="2023-12-25",
    pandas=True,
    save=True,
    storage_path="./data"
)

# Calculate bollinger bands for Polars DataFrame
pl_df = bollinger_bands(pl_df, source_column="Close")
pl_df.show(10)

# Calculate bollinger bands for Pandas DataFrame
pd_df = bollinger_bands(pd_df, source_column="Close")
pd_df.tail(10)

BOLLINGER_BANDS

Chart Parameters

The image above uses the following parameters:

Parameter	Value
`source_column`	`Close`
`period`	`20`
`std_dev`	`2`