PIL ImageFont.truetype using variable leads to the error: OSError: cannot open resource

Question

I have this code:

img = Image.new('L', (26, 17), color=255)
fnt = ImageFont.truetype('/assets/david.ttf', 23)
d = ImageDraw.Draw(img)
d.text((0, -1), "hi", font=fnt, fill=100)
img.save('newimg.png')

and it works just fine.

but what I'm trying to do, is to make a loop and in each iteration to use different font, if I change this line:

fnt = ImageFont.truetype('/assets/david.ttf', 23)

with this:

font_name = 'david.tff'
fnt = ImageFont.truetype('/assets/' + font_name, 23)

( even not in a loop )

I receive that error:

Traceback (most recent call last):
  File ".../create_dataset.py", line 30, in <module>
    fnt = ImageFont.truetype('/assets/' + font_name, 23)
  File "...\venv\lib\site-packages\PIL\ImageFont.py", line 642, in truetype
    return freetype(font)
  File "...\venv\lib\site-packages\PIL\ImageFont.py", line 639, in freetype
    return FreeTypeFont(font, size, index, encoding, layout_engine)
  File "...\venv\lib\site-packages\PIL\ImageFont.py", line 188, in __init__
    font, size, index, encoding, layout_engine=layout_engine
OSError: cannot open resource

Why using variable inside the ImageFont.truetype makes this error and how can it be solved?

Answer 1

So it took me until now, but this error occurred not because of using a variable ( which is by itself looks weird since it can be used anywhere ), but because of my misspelling:

I used david.tff instead of david.ttf