---
name: bollinger_bands
kind: function
lang: py
domain: finance
version: "1.0.0"
purity: pure
signature: "def bollinger_bands(data: list, period: int, num_std: float) -> tuple"
description: "Calcula las Bandas de Bollinger (upper, middle, lower) de una serie de precios."
tags: [finance, bollinger, volatility, indicator, python]
uses_functions: [sma_py_finance]
uses_types: []
returns: []
returns_optional: false
error_type: ""
imports: []
tested: false
tests: []
test_file_path: ""
file_path: "python/functions/finance/finance.py"
---

## Ejemplo

```python
prices = [10, 11, 12, 13, 14, 15, 14, 13, 12, 11]
upper, middle, lower = bollinger_bands(prices, 5, 2.0)
# middle es la SMA(5), upper/lower son middle +/- 2*std
```

## Notas

Retorna tupla de tres listas (upper, middle, lower). Cada lista tiene len(data) - period + 1 elementos.
La desviacion estandar se calcula sobre la ventana de tamanio period (poblacional, no muestral).
Usa internamente la funcion sma para la banda media.