Coloring digits with the listings package

I'm trying to typeset some python code, and I would like integer literals to be highlighted. I've come up, after about two hours of fighting with the documentation and various other questions here and on SO, with the following:

\lstset{ %
language=Python,
otherkeywords={1, 2, 3, 4, 5, 6, 7, 8, 9, 0},
morekeywords=[2]{1, 2, 3, 4, 5, 6, 7, 8, 9, 0},
keywordstyle=[2]{\color{orange}},
keywordstyle=\color{blue}\bfseries,
stringstyle=\color{red},
}


Unfortunately, that doesn't work. Numbers found in strings are also highlighted, which is rather annoying, and not only are they highlighted: they are highlighted in blue. Numerals in regular program text, on the other hand, are rightly highlighted in red.

Help?

EDIT: Thanks Peter Grill for your very nice solution. Is there a way to not break string colouring, though? When I use you code, the stringstyle=\color{red} doesn't seem to work anymore (strings are just plain black). Similarly, comments can be enclosed in triple quotes in python, and if I adapt your quote to detect """ blocks, then the corresponding comments are not highlighted anymore.

• While code snippets are useful, it is always best to compose a MWE that illustrates the problem including the \documentclass and the appropriate packages so that those trying to help don't have to recreate it. Nov 15 '11 at 16:53
• @lockstep Since Clément has commented already on the linked question, I don't think it's quite a duplicate. Clément, it would be helpful if you showed how the linked solution doesn't work (and give a complete example.) Nov 15 '11 at 17:37
• Hi guys, sorry for the late answer. The current answer seems perfect; sorry for not posting a MWE. Nov 16 '11 at 16:05
• @Clément Please convert your edit into a comment here, or perhaps a new question linked to this one. We like to keep questions just for that, if possible. Nov 17 '11 at 20:37

It seems that you want the coloring of the digits, but not when they are within a string. If I correctly understand, you can use a conditional to define if we should apply the color or not. Then when we encounter a quote, we disable to coloring until the next quote.

Here I have disabled coloring within both single and double quotes. If this is not desired, simply comment out the corresponding line in \lstset.

Below I have used newtoggle from the etoolbox package as I like that syntax much better than the \newif syntax. But if you don't want to include an additional package it should be pretty straightforward to adapt this to use \newif or some other conditional methods.

Further Enhancements:

• If you desire to extend this to handle floating point numbers, and highlight the decimal separator (but not periods), see Listings package: How can I format all numbers?

• A further enhancement would be to disable the coloring within comments in the code. However, this is dependent on the particular language being typeset, but a similar technique could be applied to disable coloring at the beginning of a comment and re enable it at the end of the comment. This should be straightforward for comments that have a begin and end delimiter (i.e., /* ... */ C-style comments), but for comments that go to end of line (i.e., // C-style comments), the end of line will need to be detected and used to re enable comments.

Code:

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

\newtoggle{InString}{}% Keep track of if we are within a string
\togglefalse{InString}% Assume not initally in string

\newcommand*{\ColorIfNotInString}[1]{\iftoggle{InString}{#1}{\color{red}#1}}%
\newcommand*{\ProcessQuote}[1]{#1\iftoggle{InString}{\global\togglefalse{InString}}{\global\toggletrue{InString}}}%
\lstset{literate=%
{"}{{{\ProcessQuote{"}}}}1% Disable coloring within double quotes
{'}{{{\ProcessQuote{'}}}}1% Disable coloring within single quote
{0}{{{\ColorIfNotInString{0}}}}1
{1}{{{\ColorIfNotInString{1}}}}1
{2}{{{\ColorIfNotInString{2}}}}1
{3}{{{\ColorIfNotInString{3}}}}1
{4}{{{\ColorIfNotInString{4}}}}1
{5}{{{\ColorIfNotInString{5}}}}1
{6}{{{\ColorIfNotInString{6}}}}1
{7}{{{\ColorIfNotInString{7}}}}1
{8}{{{\ColorIfNotInString{8}}}}1
{9}{{{\ColorIfNotInString{9}}}}1
}
\begin{document}
\begin{lstlisting}[basicstyle=\ttfamily]
These are colored 0123456789,
but "these are not 0123456789"
and 'these also are not 0123456789'
again colored: 0123456789
\end{lstlisting}
\end{document}

• I think it's a great idea to have a toggle. However, I would image such a toggle to not be printed in the text since it merely represents a toggle. As such, it would probably some character that is not often used in the language. This is user-specific though. Nov 15 '11 at 19:01
• @Werner: Sorry, I do not understand what you mean by "such a toggle to not be printed in the text"? The intent here was to exclude coloring of digits in strings, so " defines the begin and end of a string. Nov 15 '11 at 19:08
• Mmmm, I thought strings here might refer to keywords like myvar1 or func123 and the like. I may have been mistaken. Nov 15 '11 at 19:10
• Wow. Thanks for this thorough and detailed answer. I'll try it immediately. Nov 16 '11 at 16:08
• @Clément: Sorry, I did not understand what you had wanted earlier (seem obvious now that I see the other question). That is one reason why it is always best to compose a fully compilable MWE instead of "describing" the symptom. Jan 31 '12 at 18:42

Here is a way of applying a style to digits (only outside strings and comments), that improves upon Peter Grill's approach in two ways.

1. It is more flexible insofar as it allows you to specify additional replacements (of <= by $\leq$, for instance) to take effect everywhere in the code; that's handy because, in practice, you may want at least some literate replacements to also take place in comments (in particular) and in strings.
2. It is more robust insofar as it will work "out of the box", no matter how you define your string and comment delimiters.

\documentclass{article}

\usepackage{xcolor}
\usepackage{listings}

\newcommand\digitstyle{\color{red}}
\makeatletter
\newcommand{\ProcessDigit}[1]
{%
\ifnum\lst@mode=\lst@Pmode\relax%
{\digitstyle #1}%
\else
#1%
\fi
}
\makeatother
\lstset{literate=
{0}{{{\ProcessDigit{0}}}}1
{1}{{{\ProcessDigit{1}}}}1
{2}{{{\ProcessDigit{2}}}}1
{3}{{{\ProcessDigit{3}}}}1
{4}{{{\ProcessDigit{4}}}}1
{5}{{{\ProcessDigit{5}}}}1
{6}{{{\ProcessDigit{6}}}}1
{7}{{{\ProcessDigit{7}}}}1
{8}{{{\ProcessDigit{8}}}}1
{9}{{{\ProcessDigit{9}}}}1
{<=}{{$$\leq$$}}1,
morestring=[b]",
morestring=[b]',
morecomment=[l]//,
}
\begin{document}
\begin{lstlisting}[basicstyle=\ttfamily]
These are colored 0123456789,
but "these are not 0123456789"
and 'these also are not 0123456789'
again colored: 0123456789
// not colored: 0123456789