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Re: exporting nested list to CSV file
From: |
Christopher Howard |
Subject: |
Re: exporting nested list to CSV file |
Date: |
Tue, 22 Jul 2014 14:25:17 -0800 |
On Tue, 22 Jul 2014 21:35:35 +0200
Thorsten Jolitz <tjolitz@gmail.com> wrote:
> Christopher Howard <cmhoward2@alaska.edu> writes:
>
> > Hi. I've been using the pcsv library to parse data from external CSV
> > files, then using various elisp functions to filter/munge the
> > data. Afterwards, I was sad to discover that pcsv does not have any
> > functions for /writing/ data back to a CSV file.
> >
> > Since the data is well-structured, presumably this shouldn't be hard
> > to do. Could I get some guidance on what would be the simplest
> > approach? Is there another library I've overlooked? Or some
> > built-ins that would be especially helpful? The data are in lists
> > like so:
> >
> > (("row0datastring", "row0datastring", "row0datastring", ...)
> > ("row1datastring", "row1datastring", "row1datastring", ...)
> > ...
> > )
>
> try something like:
>
> #+begin_src emacs-lisp
> (mapconcat
> 'identity
> (append
> '("row0datastring" "row0datastring" "row0datastring")
> '("row1datastring" "row1datastring" "row1datastring")) ",")
> #+end_src
>
> #+results:
> :
> row0datastring,row0datastring,row0datastring,row1datastring,row1datastring,row1datastring
>
Thank you for helping me get started. I also needed to address the
issues of 1) newlines at the end of rows and 2) character escaping. To
address the second issue, I used "prin1", which I hope is a good
enough hack for my purposes:
#+begin_src emacs-lisp
(defun to-csv-row (fields)
(mapconcat 'prin1-to-string fields ","))
(defun to-csv-string (nested-list)
(mapconcat 'to-csv-row nested-list "\n"))
(defun to-csv-file (path nested-list)
"Converts NESTED-LIST to csv format and exports to file. NESTED-LIST is
expected to be the structure provided by the pcsv library."
(with-temp-file path
(insert (to-csv-string nested-list))))
#+end_src