Default word regex and snake_case checking

[DimitriPapadopoulos]

The underscore (_) is part of \w. From https://docs.python.org/3/library/re.html#regular-expression-syntax:

\w

For Unicode (str) patterns:
Matches Unicode word characters; this includes alphanumeric characters (as defined by str.isalnum()) as well as the underscore (_). If the ASCII flag is used, only [a-zA-Z0-9_] is matched.

For 8-bit (bytes) patterns:
Matches characters considered alphanumeric in the ASCII character set; this is equivalent to [a-zA-Z0-9_]. If the LOCALE flag is used, matches characters considered alphanumeric in the current locale and the underscore.

Is there an easy way to get \w except _ in the non-ASCII case? It would help checking snake_case.

codespell/codespell_lib/_codespell.py

Line 31 in ec0a5b9

word_regex_def = "[\\w\\-'’`]+"

[DimitriPapadopoulos]

Unicode regexes with set operations might help, but they are not available in Python yet. From https://docs.python.org/3/library/re.html#regular-expression-syntax:

• Support of nested sets and set operations as in Unicode Technical Standard #18 might be added in the future. This would change the syntax, so to facilitate this change a FutureWarning will be raised in ambiguous cases for the time being. That includes sets starting with a literal '[' or containing literal character sequences '--', '&&', '~~', and '||'. To avoid a warning escape them with a backslash.

[DimitriPapadopoulos]

• Exclude characters from a character class
• Intersection of Two Regex Classes

[DimitriPapadopoulos]

Duplicate of #2730.