Cfrgtkky

How can I read columns from a external csv file using a foreach statement? e.g. if the content of the csv file is as follows:

{0,0,0},black,

{1,1,0},yellow,

{1,0,1},pink

And I would like to use it as in the following code.

documentclass{standalone}

usepackage{tikz}

begin{document}

  foreach code/col in {%

  {0,0,0}/black,

  {1,1,0}/yellow,

  {1,0,1}/pink

  }{

   definecolor{tempcolor}{rgb}{code}

   textcolor{tempcolor}{col};

  }

  end{document}

As long as it is ensured that each line of your .csv-file is exactly of pattern

{⟨rgb-specification⟩},⟨name of color⟩,

and that there are no spaces at the commas that separate the {⟨rgb-specification⟩} from the ⟨name of color⟩, you can:

• use the catchfile-package for getting the content of the .csv-file into a temporary macro.


• Then can apply some replacement-routine, e.g., of the xstring package, to the tokens that form the expansion/replacement-text of that temporary macro.


• After that you can "feed" the expansion of the temporary macro to foreach.

documentclass{standalone}

usepackage{tikz}

usepackage{xstring}

usepackage{catchfile}



newcommandPassFirstToSecond[2]{#2{#1}}



% !!! This will produce a text-file colorlist.csv for you.!!!

% !!! Make sure it won't override another already existing!!!

% !!! file of same name !!!

begin{filecontents*}{colorlist.csv}

{0,0,0},black,

{1,1,0},yellow,

{1,0,1},pink

end{filecontents*}



begin{document}



CatchFileDef{tempa}{colorlist.csv}{}%



% Due to LaTeX's reading-apparatus which has that nice `endlinechar`-thingie,

% reading and tokenizing colorlist.csv yields that each end of a line of

% colorlist.csv will result in the insertion of an explicit space token into

% the token stream.

% Thus the comma-character-tokens that stem from the commas at the ends of lines

% will be trailed by explicit space tokens while the comma-character-tokens that

% stem from commas not at the ends of lines don't have these trailing space tokens.

% The ending of the last line of colorlist.csv does also yield the insertion

% of an explicit space token.

% Anything nested inside curly braces is protected from being replaced by

% StrSubstitute.



% Let's replace the commas at line endings by //:

expandafterStrSubstituteexpandafter{tempa}{, }{//}[tempa]%

%showtempa

% Let's replace the commas not at line endings by /:

expandafterStrSubstituteexpandafter{tempa}{,}{/}[tempa]%

%showtempa

% Let's replace the line endings (they are now denoted by //) by commas:

expandafterStrSubstituteexpandafter{tempa}{//}{,}[tempa]%

%showtempa

% Let's remove all remaining space-tokens - this does remove

% the space that came into being due to the end of the last

% line of colorlist.csv

expandafterStrSubstituteexpandafter{tempa}{ }{}[tempa]%

%showtempa





expandafterPassFirstToSecondexpandafter{tempa}{foreachcode/col in}{%

  definecolor{tempcolor}{rgb}{code}%

  textcolor{tempcolor}{col};

}%



end{document}

This assumes that the rows in the CSV file have the same number of nonempty items (trailing commas allowed).

We read one row at a time and pass it for processing; the row is split at commas (ignoring empty lines), the items so obtained are braced and passed as arguments to the macro specified in the second argument to readcsv. Such a macro should have the exact number of arguments as the columns in the CSV file.

I provide two examples.

begin{filecontents*}{jobname.csv}

{0,0,0},black,

{0,1,1},cyan,

{1,0,1},pink

end{filecontents*}



begin{filecontents*}{jobname2.csv}

{0,0,0},black,nero

{0,1,1},cyan,ciano

{1,0,1},pink,rosa

end{filecontents*}



documentclass{article}

usepackage{xcolor}

usepackage{xparse}



ExplSyntaxOn

NewDocumentCommand{readcsv}{mm}

 {% #1 = filename, #2 = macro to apply to each row

  tonytan_readcsv:nn { #1 } { #2 }

 }



ior_new:N g_tonytan_readcsv_stream

seq_new:N l__tonytan_readcsv_temp_seq

tl_new:N l__tonytan_readcsv_temp_tl



cs_new_protected:Nn tonytan_readcsv:nn

 {

  ior_open:Nn g_tonytan_readcsv_stream { #1 }

  ior_map_inline:Nn g_tonytan_readcsv_stream

   {

    tonytan_readcsv_generic:Nn #2 { ##1 }

   }

  ior_close:N g_tonytan_readcsv_stream

 }

cs_new_protected:Nn tonytan_readcsv_generic:Nn

 {

  seq_set_from_clist:Nn l__tonytan_readcsv_temp_seq { #2 }

  tl_set:Nx l__tonytan_readcsv_temp_tl

   {

    seq_map_function:NN l__tonytan_readcsv_temp_seq __tonytan_readcsv_brace:n

   }

  exp_last_unbraced:NV #1 l__tonytan_readcsv_temp_tl

 }

cs_new:Nn __tonytan_readcsv_brace:n { {#1} }

ExplSyntaxOff



newcommand{showcolor}[2]{textcolor[rgb]{#1}{#2}par}



newcommand{showcolorx}[3]{textcolor[rgb]{#1}{#2} (#3)par}



begin{document}



readcsv{jobname.csv}{showcolor}



readcsv{jobname2.csv}{showcolorx}



end{document}

Here, I use readarray to get the file into a def and then listofitems (included in readarray) to parse it and loop over it.

documentclass{standalone}

usepackage{tikz,readarray,filecontents}

begin{filecontents*}{mydata.csv}

{0,0,0},black,

{1,1,0},yellow,

{1,0,1},pink

end{filecontents*}

begin{document}

  readarraysepchar{\}%

  readdef{mydata.csv}mydata%

  ignoreemptyitems%

  setsepchar{\/,}%

  readlistmylist{mydata}%

  foreachitemxinmylist{%

    deftmp{definecolor{tempcolor}{rgb}}%

    expandafterexpandafterexpandaftertmpmylist[xcnt,1]%

    textcolor{tempcolor}{mylist[xcnt,2]};%

  }

  end{document}

After playing with it for a while, I think that datatool is a better tool for what I need. Thanks everyone for helping!

documentclass{standalone}

usepackage{tikz,datatool,filecontents}

begin{filecontents*}{mydata.csv}

   code,text,

  {0,0,0},black,

  {1,1,0},yellow,

  {1,0,1},pink

end{filecontents*}

DTLsetseparator{,}

DTLloaddb{myfile}{mydata.csv}

begin{document}

DTLforeach*

   {myfile}

   {code=code,text=text}% assignment

   {% Stuff to do at each iteration:

   expandafterexpandafterdefinecolor{tempcolor}{rgb}{code}

   textcolor{tempcolor}{text} 

 }

 end{document}