How to emphasize with in a listing an identifier containing a digit?

Question

I have this LaTeX code that I want to typeset using listings:

\documentclass[paper=a4,fontsize=12pt,version=last]{scrlttr2}

I want to emphasize "scrlttr2" with a different format. How can it be done with listings?

Answer 1

You must set scrlttr2 as a keyword. The digit in the keyword need a special handling. You need otherkeyword

\listfiles
\documentclass{article}
\usepackage{color}
\usepackage{listings} 
\lstset{language=[LaTeX]tex,
       otherkeywords={scrlttr2},
       morekeywords=[2]{scrlttr2},
       keywordstyle=[2]{\color{red}\large}
       }

\begin{document}
\begin{lstlisting}
\documentclass[paper=a4,fontsize=12pt,version=last]{scrlttr2}
\end{lstlisting}
\end{document}

Answer 2

You can also use one escaping character. I use ⠶ because it is not used in listings.

\documentclass{article}
    \usepackage{listings}
    \usepackage{xcolor}

\begin{document}
    \lstset{escapechar=\⠶}  % Any UTF-8 character can be used.
    \lstset{language=Python}
    \begin{lstlisting}
for i in range(5):
    ⠶\textcolor{red}{print}⠶(i)
print('Fin de la boucle...')
    \end{lstlisting}

    \lstset{escapechar={}} % If necessary, we can delete the special escaping character.
    \begin{lstlisting}
for i in range(5):
    ⠶\textcolor{red}{print}⠶(i)
print('Fin de la boucle...')
    \end{lstlisting}

\end{document}

Answer 3

More generally: if you want to emphasize everything between pairs of braces (and accounting for nested braces), you can define them as a special type of "comment". You can do this for other "spans" of characters which you would like to be typeset differently, such as math-mode elements.

\documentclass{article}
\usepackage{color}
\usepackage{listings} 
\lstset{
  language=[LaTeX]tex,
  morecomment=[n][\color{blue!50!black}\bfseries]{\{}{\}},
  morecomment=[s][\color{green!50!black}\bfseries\slshape]{$}{$},
}

\begin{document}
\begin{lstlisting}
\documentclass[paper=a4,fontsize=12pt,version=last]{scrlttr2}
\begin{document}
Pythagoras' Theorem: $a^2 + b^2 = c^2$
\end{document}
\end{lstlisting}
\end{document}

Result:

The "interpretation" of these spans as somehow being "comments" is incidental; what matters is that it allows you to set the formatting.