[Python] Psychopy TextStim does not display the blank spaces correctly in the multiline string...

I am trying to display three lines of text as part of a stimulus using Psychopy. The first and third rows contain randomly generated words (from a dictionary of common words) and the middle row contains a trigram that's position varies depending on an integer value passed into the function. Each row contains exactly 15 characters and the middle row includes the trigram surrounded by blank spaces (its position varies). When I print the string to the terminal it always displays correctly but not when assigned to TextStim.

At the bottom, I've included a modified version that surrounds the trigram with words and a single space in between that works. However, I am hoping to understand why this first version does not work. I just cannot figure out what is causing the error (pictures of how the error affects the display are included below)

from psychopy import visual, event
import random
import csv
from numpy.random import multinomial

# creating the dictionary from a file
def word_dict(file):
wordlist = []
input_file = open(file)
reader = csv.reader(input_file, delimiter = ',')
next(reader)
for row in reader:
for word in row:
wordlist.append(word)
input_file.close()

words = {len(word) : [] for word in wordlist}
for word in wordlist:
words[len(word)].append(word)

return words

test_dict = word_dict("wordlist.csv")

# this function generates text stimuli for the top and bottom rows in the string.
# first determines how many words and then randomly selects words of appropriate length
def random_string(words: dict):
n = random.randint(2,4)
if n == 2:
while True:
numbers = multinomial(14, [1/2.] * 2) # determines word length
if 0 not in numbers:
break
string = (f"{random.choice(words[numbers[0]])} "
f"{random.choice(words[numbers[1]])}")
elif n == 3:
while True:
numbers = multinomial(13, [1/3.] * 3)
if 0 not in numbers:
break
string = (f"{random.choice(words[numbers[0]])} "
f"{random.choice(words[numbers[1]])} "
f"{random.choice(words[numbers[2]])}")
elif n == 4:
while True:
numbers = multinomial(12, [1/4.] * 4)
if 0 not in numbers:
break
string = (f"{random.choice(words[numbers[0]])} "
f"{random.choice(words[numbers[1]])} "
f"{random.choice(words[numbers[2]])} "
f"{random.choice(words[numbers[3]])}")

return string

# The string that is assigned to the textStim is generated with the following function
def generate_stimuli(pos, type):
if type == "cue":
stimulus = "###"
elif type == "target":
# Generate random letters for the middle row
letter1 = chr(random.randint(ord('a'), ord('z')))
letter2 = chr(random.randint(ord('a'), ord('z')))
letter3 = chr(random.randint(ord('a'), ord('z')))
stimulus = letter1 + letter2 + letter3

# set the position for the middle row
right_side = 13 - pos
left_side = 12 - right_side
center_string = (left_side * " ") + stimulus + (right_side * " ")

# create random strings for above and below the target
above = random_string(test_dict) # text_dict is dictionary of common words
below = random_string(test_dict) # text_dict is dictionary of common words
if type == "cue":
return center_string
elif type == "target":
return (above + '\n' + center_string + '\n' + below)

# If I call the above function and then print the result it works correctly.
# The only problem is when I pass it to the text object in visual.TextStim

win = visual.Window(
fullscr=True,
size=[1920, 1080],
screen=0,
color=[+1] * 3,
units="deg"
)

target_string = visual.TextStim(
win=win,
anchorHoriz="center",
anchorVert="center",
font="courier new",
color=[-1] * 3,
units="deg",
height=1.2
)

stimulus = generate_stimuli(1, "target")
target_string.text = stimulus

target_string.draw()
win.flip()
event.waitKeys()

win.close()


Essentially, I should be passing a string with three lines of exactly 15 characters into the TextStim but the middle row keeps displaying incorrectly.

If I replace center_string = (left_side * " ") + stimulus + (right_side * " ") with center_string = (left_side * "*") + stimulus + (right_side * "*") it displays correctly. but if I revert to the empty spaces, it does not again

using "*" with position == 1 Using " " with position == 1

I just cannot seem to understand why it does not display correctly with the empty spaces. Could anchorHoriz be centering each row independently and some of the spaces are not carrying through? I still can't seem to understand after reviewing the classes code.

The modified version below works fine but I am still trying to understand why the above does not work

def random_word(length: int, words: dict):
word_length = length - 1
return random.choice(words[word_length])

def generate_stimuli(pos, type):
if type == "cue":
stimulus = "###"
elif type == "target":
# Generate random letters for the trigram
letter1 = chr(random.randint(ord('a'), ord('z')))
letter2 = chr(random.randint(ord('a'), ord('z')))
letter3 = chr(random.randint(ord('a'), ord('z')))
stimulus = letter1 + letter2 + letter3

# set the position for the stimuli
right_side = 13 - pos
left_side = 12 - right_side

# select words for the right and left sides
if right_side > 1:
word_right = random_word(right_side, test_dict)
else:
word_right = " "

if left_side > 1:
word_left = random_word(left_side, test_dict)
else:
word_left = ""

if type == "cue":
center_string = (left_side * " ") + stimulus + (right_side * " ")
elif type == "target":
if pos == 1:
center_string = f"{stimulus} {word_right}"
elif pos == 14:
center_string = f"{word_left} {stimulus}"
else:
center_string = f"{word_left} {stimulus} {word_right}"

# create random strings for above and below the trigram
above = random_string(test_dict)
below = random_string(test_dict)

if type == "cue":
return center_string
elif type == "target":
return (above + '\n' + center_string + '\n' + below)

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