Watch commas in Python lists of strings!

This may yield a hard-to-catch bug (check missing comma between ‘2’ and ‘3’ in the second assignment:

➜ python3
Python 3.10.6 | packaged by conda-forge | (main, Aug 22 2022, 20:38:29) [Clang 13.0.1 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> a = [1, 2 3, 4]
  File "<stdin>", line 1
    a = [1, 2 3, 4]
            ^^^
SyntaxError: invalid syntax. Perhaps you forgot a comma?
>>> a = ['1', '2' '3', '4']
>>> a
['1', '23', '4']
>>>