Extract cited bibtex keys from tex file using regex in python

Question

I'm trying to extract cited BibTeX keys from a LaTeX document using regex in python.

I'd like to exclude the citation if it is commented out (% in front) but still include it if there is a percent sign (\%) in front.

Here is what I came up with so far:

\\(?:no|)cite\w*\{(.*?)\}

An example to try it out:

blablabla
Author et. al \cite{author92} bla bla. % should match
\citep{author93} % should match
\nocite{author94} % should match
100\%\nocite{author95} % should match
100\% \nocite{author95} % should match
%\nocite{author96} % should not match
\cite{author97, author98, author99} % should match
\nocite{*} % should not match

Regex101 testing: https://regex101.com/r/ZaI8kG/2/

I appreciate any help.

Answer 1

Use the newer regex module (pip install regex) with the following expression:

(?<!\\)%.+(*SKIP)(*FAIL)|\\(?:no)?citep?\{(?P<author>(?!\*)[^{}]+)\}

See a demo on regex101.com.

---

More verbose:

(?<!\\)%.+(*SKIP)(*FAIL)     # % (not preceded by \) 
                             # and the whole line shall fail
|                            # or
\\(?:no)?citep?              # \nocite, \cite or \citep
\{                           # { literally
    (?P<author>(?!\*)[^{}]+) # must not start with a star
\}                           # } literally

---

If installing another library is not an option, you need to change the expression to

(?<!\\)%.+
|
(\\(?:no)?citep?
\{
    ((?!\*)[^{}]+)
\})

and need to check programatically if the second capture group has been set (is not empty, that is).
The latter could be in Python:

import re

latex = r"""
blablabla
Author et. al \cite{author92} bla bla. % should match
\citep{author93} % should match
\nocite{author94} % should match
100\%\nocite{author95} % should match
100\% \nocite{author95} % should match
%\nocite{author96} % should not match
\cite{author97, author98, author99} % should match
\nocite{*} % should not match
"""

rx = re.compile(r'''(?<!\\)%.+|(\\(?:no)?citep?\{((?!\*)[^{}]+)\})''')

authors = [m.group(2) for m in rx.finditer(latex) if m.group(2)]
print(authors)

Which yields

['author92', 'author93', 'author94', 'author95', 'author95', 'author97, author98, author99']