Match LaTeX reserved characters with regex
latex, python, regex
Solution
The `[^\]` is a character class for anything not a `\`, that is why it is matching everything. You want a negative lookbehind assertion:
((?<!\)[#\$%\^&_\{\}~\\])
`(?<!...)` will match whatever follows it as long as `...` is not in front of it. You can check this out at the python docs
Problem
I have an HTML to LaTeX parser tailored to what it's supposed to do (convert snippets of HTML into snippets of LaTeX), but there is a little issue with filling in variables. The issue is that variables should be allowed to contain the LaTeX reserved characters (namely `# $ % ^ & _ { } ~ \`). These need to be escaped so that they won't kill our LaTeX renderer. The program that handles the conversion and everything is written in Python, so I tried to find a nice solution. My first idea was to simply do a `.replace()`, but replace doesn't allow you to match only if the first is not a `\`. My second attempt was a regex, but I failed miserably at that. The regex I came up with is `([^\][#\$%\^&_\{\}~\\])`. I hoped that this would match any of the reserved characters, but only if it didn't have a `\` in front. Unfortunately, this matches ever single character in my input text. I've also tried different variations on this regex, but I can't get it to work. The variations mainly consisted of removing/adding slashes in the second part of the regex. Can anyone help with this regex? EDIT Whoops, I seem to have included the slashes as well. Shows how awake I was when I posted this :) They shouldn't be escaped in my case, but it's relatively easy to remove them from the regexes in the answers. Thanks all!