TA-Lib Function & Abstract API 2018-09-26

Function API Examples

Similar to TA-Lib, the function interface provides a lightweight wrapper of the exposed TA-Lib indicators.

Each function returns an output array and have default values for their parameters, unless specified as keyword arguments. Typically, these functions will have an initial "lookback" period (a required number of observations before an output is generated) set to NaN.

All of the following examples use the function API:

import numpy
import talib

close = numpy.random.random(100)

Calculate a simple moving average of the close prices:

output = talib.SMA(close)

Calculating bollinger bands, with triple exponential moving average:

from talib import MA_Type

upper, middle, lower = talib.BBANDS(close, matype=MA_Type.T3)

Calculating momentum of the close prices, with a time period of 5:

output = talib.MOM(close, timeperiod=5)

Abstract API Quick Start

If you're already familiar with using the function API, you should feel right at home using the abstract API. Every function takes the same input, passed as a dictionary of Numpy arrays:

import numpy as np
# note that all ndarrays must be the same length!
inputs = {
    'open': np.random.random(100),
    'high': np.random.random(100),
    'low': np.random.random(100),
    'close': np.random.random(100),
    'volume': np.random.random(100)
}

Functions can either be imported directly or instantiated by name:

from talib import abstract
sma = abstract.SMA
sma = abstract.Function('sma')

From there, calling functions is basically the same as the function API:

from talib.abstract import *
output = SMA(input_arrays, timeperiod=25) # calculate on close prices by default
output = SMA(input_arrays, timeperiod=25, price='open') # calculate on opens
upper, middle, lower = BBANDS(input_arrays, 20, 2, 2)
slowk, slowd = STOCH(input_arrays, 5, 3, 0, 3, 0) # uses high, low, close by default
slowk, slowd = STOCH(input_arrays, 5, 3, 0, 3, 0, prices=['high', 'low', 'open'])

Advanced Usage

For more advanced use cases of TA-Lib, the Abstract API also offers much more flexibility. You can even subclass abstract.Function and override set_input_arrays to customize the type of input data Function accepts (e.g. a pandas DataFrame).

Details about every function can be accessed via the info property:

print Function('stoch').info
{
  'name': 'STOCH',
  'display_name': 'Stochastic',
  'group': 'Momentum Indicators',
  'input_names': OrderedDict([
    ('prices', ['high', 'low', 'close']),
  ]),
  'parameters': OrderedDict([
    ('fastk_period', 5),
    ('slowk_period', 3),
    ('slowk_matype', 0),
    ('slowd_period', 3),
    ('slowd_matype', 0),
  ]),
  'output_names': ['slowk', 'slowd'],
}

Or in human-readable format:

help(STOCH)
str(STOCH)

Other useful properties of Function:

Function('x').function_flags
Function('x').input_names
Function('x').input_arrays
Function('x').parameters
Function('x').lookback
Function('x').output_names
Function('x').output_flags
Function('x').outputs

Aside from calling the function directly, Functions maintain state and will remember their parameters/input_arrays after they've been set. You can set parameters and recalculate with new input data using run():

SMA.parameters = {'timeperiod': 15}
result1 = SMA.run(input_arrays1)
result2 = SMA.run(input_arrays2)

# Or set input_arrays and change the parameters:

SMA.input_arrays = input_arrays1
ma10 = SMA(timeperiod=10)
ma20 = SMA(20)