Preloading stimuli in code
Sometimes I want to load the stimuli before the main loop starts, so that I can, for example, insert prospective memory targets or N-Back trials, or apply constraints to the randomisation. The easiest way to do this is to use add a trial handler in a code component. This solution is taken from my PsychoPy Code Component Snippets - Google Docs.
In Python, the code for a trial handler is:
myData = data.TrialHandler(
nReps=1,
method='sequential', # or 'random'
extraInfo=expInfo,
originPath=-1,
trialList=data.importConditions('conditions.xlsx'), # Add ", selection=useRows" inside the brackets for selected rows
seed=None,
name='myData')
# Add the following for random
sequenceIndices = [ ]
for Idx in myData.sequenceIndices:
sequenceIndices.append( Idx[0] )
This auto translates to:
myData = new data.TrialHandler({
"nReps": 1,
"method": "sequential",
"extraInfo": expInfo,
"originPath": (- 1),
"trialList": data.importConditions("conditions.xlsx"),
"seed": null,
"name": "myData"});
However, the correct translation is:
myData = new TrialHandler({
psychoJS: psychoJS,
nReps: 1,
method: TrialHandler.Method.SEQUENTIAL, // or .RANDOM
extraInfo: expInfo,
originPath: undefined,
trialList: 'conditions.xlsx',
// or trialList: TrialHandler.importConditions(psychoJS.serverManager, 'conditions.xlsx', useRows),
seed: undefined,
name: 'myData'});
// Add the following for random
sequenceIndices = myData._trialSequence[0];
Access individual values using: aValue = myData.trialList[Idx]['variableName'] for sequential and aValue = myData.trialList[sequenceIndices[Idx]]['variableName'] for random.
The spreadsheet can be replaced with a list of dictionaries, e.g.
conditions=[ ]
for Idx in range (10):
conditions.append({"cue_ori": 10*Idx, "target_x": 300*(Idx%2)})