StimulusSelector class

This object keeps several expyriment stimuli, and can define one of them as active.

You can then handle the active stimulus: present it, modify its position.

Using this class

This class is useful when you have a stimulus that can change during a trial, and you want to change the stimulus independently of presenting and moving it. For example, suppose a moving rectangle should repeatedly changes its color between red and green according to some logic. You can:

• Define two rectangles with the same size, one red and one green (this is better than repeatedly changing the color of a single rectangle: replotting the stimulus on every frame would be time-consuming)
• Create a StimulusSelector
• Add the two rectangles to the selector using StimulusSelector.add_stimulus
• To move the rectangle, change StimulusSelector.position.
• To change the rectangle color, use StimulusSelector.activate.

Methods and properties:

class trajtracker.stimuli.StimulusSelector(stimuli=())

__init__(stimuli=())

Constructor - invoked when you create a new object by writing ChangingStimulus()

Parameters:stimuli – A list of stimuli to add. Each entry in the list is a (key, stimulus) pair - see add_stimulus()

activate(key)

Set one of the stimuli as the active one.

Parameters:key – The key of the stimulus, as set in add_stimulus()

active_stimulus

Get the expyriment stimulus currently active

add_stimulus(key, stim)

Add a stimulus

Parameters:

• key – Identifier (logical name) for this stimulus
• stim – The actual expyriment stimulus

log_level

Logging level of this object: trajtracker.log_none, log_error (default), log_warn, log_info, log_debug, log_trace

offset_event

The time when the object should disappear from screen.

Type:Event, or None to avoid automatic offset.

onset_event

The time when the object should appear on screen.

Type:Event, or None to avoid automatic onset.

position

The position of the active stimulus. When you update this, positions of all stimuli will be updated.

present(clear=True, update=True)

present the active stimulus :return: The function’s running time