Command for comma in math or text mode

Question

I have the following csv file (myCSVfile.csv) which contains header with LaTeX code:

$T_{1,2}$,	$T_{3}$
100,	300
200,	500

In my LaTeX document, I import this table with \pgfplotstabletypeset[col sep=comma,row sep=newline]{myCSVfile.csv}.

It works well but my csv file is not satisfying for me because some comma are note column separators but just characters in a math expression in header titles, as in: $T_{1,2}$

I there a native command that just print a comma in math mode, e.g.: $T_{1\comma{}2}$ instead of $T_{1,2}$ which output nearly the same in the pdf ?. In text mode it would also be OK for me even if it's not the best solution: $T_{1\text{\comma{}}2}$.

I found the \mathpunct command here but there is still a comma when I use it in the csv file : $T_{1\mathpunct{,}2}$ instead of $T_{1,2}$ and I get an error when importing with \pgfplotstabletypeset...

I know that I can just put my header title between double quotes "$T_{1,2}$" to be sure that the comma in header title will not be interpreted as column separator, but I wonder if there is a way to obtain a comma with a native command in math mode or even in text mode.

MWE:

\documentclass{article}
\usepackage{pgfplotstable,filecontents}
\begin{filecontents}{myCSVfile.csv}
$T_{1,2}$, $T_{3}$
100,      300

200,      500

\end{filecontents}
\begin{document}
    \pgfplotstabletypeset[col sep = comma,row sep=newline]{myCSVfile.csv}
\end{document}

Answer 1

I would use "$T_{1,2}$" as that will be easily understood by any software or human reading the csv file. However comma is ASCII decimal 44, hex 2C so you can use ^^2c if you wish:

\documentclass{article}
\usepackage{pgfplotstable,filecontents}
\begin{filecontents}{myCSVfile.csv}
$T_{1^^2c 2}$, $T_{3}$
100,      300

200,      500

\end{filecontents}
\begin{document}
    \pgfplotstabletypeset[col sep = comma,row sep=newline]{myCSVfile.csv}
\end{document}