Indicator operations

Each indicator provides operations to read, add, update and remove its values.

Reading values

Indicators implement Sequence interface, meaning they can be treated as any other list when reading data.

Following operations demonstrate how to read indicator's values:

from talipp.indicators import SMA

sma = SMA(period=3, input_values=[1,2,3])

# print all values
# outputs [None, None, 2]
print(sma)

# print last value
# outputs 2
print(sma[-1])

# print number of values
# outputs 3
print(len(sma))

Adding values

To incrementally add a new value use add method:

from talipp.indicators import SMA

sma = SMA(period=3, input_values=[1,2,3])

# add a single value
sma.add(4)

# add a list of values
sma.add([4, 5, 6])

Updating values

To update the most recent value use update method:

from talipp.indicators import SMA

sma = SMA(period=3, input_values=[1,2,3])

# update the last input value
sma.update(4)

Note

Update of a value does not change number of indicator's values. Instead, it first removes the last input value and then it appends a new one.

Removing values

Indicators provide several ways how to remove data:

1. To remove the most recent input value, use remove method:

   from talipp.indicators import SMA
   
   sma = SMA(period=3, input_values=[1,2,3])
   
   # outputs [None, None, 2]
   print(sma)
   
   # remove the last input value
   sma.remove()
   
   # outputs [None, None]
   print(sma)
   

2. To remove all input values, use remove_all method:

   from talipp.indicators import SMA
   
   sma = SMA(period=3, input_values=[1,2,3])
   
   # remove all input values
   sma.remove_all()
   
   # outputs []
   print(sma)
   

3. To remove the oldest values, use purge_oldest method:

   from talipp.indicators import SMA
   
   sma = SMA(period=3, input_values=[1,2,3])
   
   # outputs [None, None, 2]
   print(sma)
   
   # purge the first value
   sma.purge_oldest(1)
   
   # outputs [None, 2]
   print(sma)
   

Note

Purging old values is useful when memory consumption is a concern. If old indicator's values are not needed anymore, feel free to purge them. However, be careful not to purge any data if calculation of the current values still depends on them.