Basic Python Questions - Oct. 31, 2013

[Jim Gibson]

In article <OKCdnXfaQqxze-jPnZ2dnUVZ_jGdnZ2d at earthlink.com>, E.D.G.
<edgrsprj at ix.netcom.com> wrote:

>        My main, complex programs won't be run at Web sites. They will 
> instead continue to be available as downloadable exe programs.  The CGI (or 
> whatever) programming work would involve relatively simple programs. But 
> they would need to be able to generate charts that would be displayed on Web 
> pages. That sounds like it is probably fairly easy to do using Python. A 
> Perl - Gnuplot combination is also supposed to be able to do that. But so 
> far I have not seen any good explanations for how to actually get Gnuplot to 
> run as a callable CGI program. So other programs such as Python are being 
> considered.

One way to generate plot within a CGI program is this:

1. Write a file with gnuplot commands (e.g., 'gnuplot.cmd') that set
the output device to a graphics file of some format (e.g., PNG),
generate a plot, and quit gnuplot.

2. Run gnuplot and point it to the file of commands (e.g., 'gnuplot
gunplot.cmd') . How this is done depends upon the CGI program language
(see below).

3. Generate HTML that uses the generated graphics file as an embedded
image (using the <img> tag).

I have done this in the past, but not recently. This should work for
Python (os.system("gnuplot gnuplot.cmd") or Perl (system("gnuplot
gnuplot.cmd") with suitable commands to execute external programs.

-- 
Jim Gibson