According to the PEP 8 coding style guidelines, how should constant values be named in Python?
in camel case without using underscores to separate words -- e.g. maxValue = 255
maxValue = 255
in lowercase with underscores to separate words -- e.g. max_value = 255
max_value = 255
in mixed case without using underscores to separate words -- e.g. MaxValue = 255 Use an uppercase single letter, word, or words. Separate words with underscores to improve readability.
MaxValue = 255
in all caps with underscores separating words -- e.g. MAX_VALUE = 255
MAX_VALUE = 255