Re: gnulib-tool.py: Simplify regular expressions.

[Collin Funk]

On 4/11/24 12:25 PM, Bruno Haible wrote:
> Oh, this means that r'[x\$]' contains dollar and backslash, whereas the
> programmer might have thought that it contains only the dollar? Indeed,
> it's worth to listen to these warnings!

I don't think it changes the meaning:

    import re
    re.match(r'[x$]*', 'x\\$').group()
    'x'
    re.match(r'[x\$]*', 'x\\$').group()
    'x'
    re.match(r'[x\\$]*', 'x\\$').group()
    'x\\$'

Since in Python you have to backslash a backslash in string literals.
Therefore to backslash a backslash you would have to do '\\\\'. Since
we are using raw strings a backslashed backslash is r'\\'. The Python
Regular expression page has a far better explanation of that [1]. :)

    # Regular string.
    re.match('\\\\', '\\').group()
    '\\'
    print(re.match('\\\\', '\\').group())
    \
    # Raw string.
    re.match(r'\\', '\\').group()
    '\\'
    print(re.match(r'\\', '\\').group())
    \

[1] https://docs.python.org/3/library/re.html#module-re

Collin