rm-hull/luma.led_matrix

IndexError: list index out of range

perrycannon opened this issue · 5 comments

perrycannon commented

Type of Raspberry Pi

I am using a Raspberry Pi B Plus and a Raspberry Pi Zero. Same error on each.

Linux Kernel version

5.4.51+ #1333 Mon Aug 10 16:38:02 BST 2020 armv6l GNU/Linux

Expected behaviour

matrixTimeCNN.zip

This script gets the RSS feed from CNN. I cycle through to make one string of the 10 top headline titles. Save this as msg to print to the matrix led. The script has been running for 3 days with no issues. I have the same exception on the Raspberry Pi B Plus and Raspberry Pi Zero.

Actual behaviour

Traceback (most recent call last):
  File "matrixTime.py", line 75, in <module>
    demo(args.cascaded, args.block_orientation, args.rotate, args.reverse_order)
  File "matrixTime.py", line 46, in demo
    show_message(device, msg, fill="white", font=proportional(CP437_FONT), scroll_delay=0.1)
  File "/usr/local/lib/python3.7/dist-packages/luma/core/legacy/__init__.py", line 81, in show_message
    w, h = textsize(msg, font)
  File "/usr/local/lib/python3.7/dist-packages/luma/core/legacy/__init__.py", line 29, in textsize
    src = [c for ascii_code in txt for c in font[ord(ascii_code)]]
  File "/usr/local/lib/python3.7/dist-packages/luma/core/legacy/__init__.py", line 29, in <listcomp>
    src = [c for ascii_code in txt for c in font[ord(ascii_code)]]
  File "/usr/local/lib/python3.7/dist-packages/luma/core/legacy/font.py", line 44, in __getitem__
    bitmap = self.font[ascii_code]
IndexError: list index out of range

The script will of course stop after the exception. When I restart the script on both Raspberry Pi's, the exception occurs at the first instance of show_message for the CNN RSS string. The prior show_message in my script scrolls the date and time which works, no exception is returned.

I do not understand why the exception occurs?

thijstriemstra commented

the font you use probably doesn't contain all characters you're trying to display, hence the IndexError?

rm-hull commented

@thijstriemstra we could probably throw a more user-friendly error message that indicates the character that is not supported in the font

thijstriemstra commented

Sounds good.

rm-hull commented

@perrycannon i had a look at your script, and it is likely that there are unicode characters that are not supported by the bitmap font. There is a font wrapper class called tolerant which will substitute a replacement character if the relevant one is not found. Use as follows:

from luma.core.legacy.font import proportional, tolerant, CP437_FONT, TINY_FONT, SINCLAIR_FONT, LCD_FONT

...

show_message(device, msg, fill="white", font=proportional(tolerant(CP437_FONT)), scroll_delay=0.1)

See the docs for more information: https://luma-core.readthedocs.io/en/latest/legacy.html#luma.core.legacy.font.tolerant

perrycannon commented