Stack

class deeptrack.features.Stack(value: Any | Callable[[...], Any], **kwargs: Any)

Bases: Feature

Stack the input and the value.

This feature combines the output of the input data (inputs) and the value produced by the specified feature (value). The resulting output is a list where the elements of the inputs and value are concatenated.

If B is a feature, Stack can be visualized as

>>>   A >> Stack(B) = [*A(), *B()]

It is equivalent to using the & operator

>>> A & B

Parameters

value: PropertyLike[Any]

The feature or data to stack with the input data.

**kwargs: Any

Additional arguments passed to the parent Feature class.

Attributes

__distributed__: bool

Set to False, indicating that this feature’s .get() method processes the entire input at once even if it is a list, rather than distributing calls for each item of the list.

Methods

get(inputs, value, _ID, **kwargs) -> list[Any]

Concatenate the inputs with the value.

Examples

>>> import deeptrack as dt

Start by creating a pipeline using Stack:

>>> pipeline = dt.Value([1, 2, 3]) >> dt.Stack(value=[4, 5])
>>> pipeline.resolve()
[1, 2, 3, 4, 5]

Equivalently, this pipeline can be created using:

>>> pipeline = dt.Value([1, 2, 3]) & [4, 5]
>>> pipeline.resolve()
[1, 2, 3, 4, 5]

Or:

>>> pipeline = [4, 5] & dt.Value([1, 2, 3])  # Different result
>>> pipeline.resolve()
[4, 5, 1, 2, 3]

Note

If a feature is called directly, its result is cached internally. This can affect how it behaves when reused in chained pipelines. For example:

>>> stack_feature = dt.Stack(value=2)
>>> _ = stack_feature(1)  # Evaluate the feature and cache the output
>>> (1 & stack_feature)()
[1, 1, 2]

To ensure consistent behavior when reusing a feature after calling it, reset its state using instead:

>>> stack_feature = dt.Stack(value=2)
>>> _ = stack_feature(1)
>>> stack_feature.update()  # clear cached state
>>> (1 & stack_feature)()
[1, 2]

Methods Summary

get(inputs, value, **kwargs)

Concatenate the input with the value.

Methods Documentation

get(inputs: Any | list[Any], value: Any | list[Any], **kwargs: Any) → list[Any]

Concatenate the input with the value.

It ensures that both the input (inputs) and the value (value) are treated as lists before concatenation.

Parameters

inputs: Any or list[Any]

The input data to stack. Can be a single element or a list.

value: Any or list[Any]

The feature or data to stack with the input. Can be a single element or a list.

**kwargs: Any

Additional keyword arguments (not used here).

Returns

list[Any]

A list containing all elements from image and value.