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stringlistpsychopyformatted

Formatted String from List Psychopy

My task is a variation of a multiple object tracking task. There are 7 circles on the screen. It randomly selects 3 circles to change the color (red, green, blue) briefly to indicate to the participant to track these circles. After the color change, all the circles will change to the same color and the circles will move for a period of time. When the circles stop moving, a response prompt will appear, where the participant is to select one of the three colored circles ('select the red/green/blue circle'). I am having difficulty inserting which color circle to select into the formatted string. I keep getting the error message: unsupported operand type(s) for %: 'TextStim' and 'list'

I'm not sure if I need to or how to convert these lists, so any help would be much appreciated!

n_targets = 7 #seven locations     
circles = [] #setting up the circle stimuli
for i in range(n_targets):
    tmp = visual.Circle(win,radius = 27,units = 'pix',edges = 32,fillColor='white',lineColor = 'black',lineWidth = 1, pos=(posx[i],posy[i]))
circles.append(tmp)
cols = ['blue','red','green'] #3 colors the circles will change to 
targets = random.sample(circles,3) #randomly select 3 of the 7 circles
TrialTarget = random.sample(targets, 1) #select 1 of the 3 circles to be the target for the trial 
#code for movement would go here (skipping since it is not relevant)
#at end of trial, response prompt appears and ask user to select target and is where error occurs
ResponsePrompt = visual.TextStim(win, text = "Select the %s circle") %TrialTarget
Solution

  • In this line, you are trying to create a formatted string from a TextStim object and a Circle stimulus object rather than a string object and another string object:

    ResponsePrompt = visual.TextStim(win, text = "Select the %s circle") %TrialTarget

    i.e. ResponsePrompt is clearly a visual.TextStim, as you are creating it as one, and I think TrialTarget is a visual.Circle stimulus, as you randomly sample it from a list of Circles.

    I'm guessing that you actually want to incorporate the colour label into the prompt text. So to fix both problems (the type incompatibility and the formatting syntax), you need to actually get one of the elements of cols, called say trialColour, and use something like this:

    ResponsePrompt = visual.TextStim(win, text = "Select the %s circle" % trialColour)

    i.e. here trialColour is actually a string, and the formatting operation is brought inside the brackets so it applies directly to the text string "Select the %s circle"

    That should hopefully fix your immediate problem. You might also want to investigate using random.shuffle() to shuffle lists in place instead of random.sample().