Calling gnuplot from python

Question

I\'ve a python script that after some computing will generate two data files formatted as gnuplot input.

How do I \'call\' gnuplot from python ?

I want to se

Answer 1

I was trying to do something similar, but additionally I wanted to feed data from within python and output the graph file as a variable (so neither the data nor the graph are actual files). This is what I came up with:

#! /usr/bin/env python

import subprocess
from sys import stdout, stderr
from os import linesep as nl

def gnuplot_ExecuteCommands(commands, data):
    args = ["gnuplot", "-e", (";".join([str(c) for c in commands]))]
    program = subprocess.Popen(\
        args, \
        stdin=subprocess.PIPE, \
        stdout=subprocess.PIPE, \
        stderr=subprocess.PIPE, \
        )
    for line in data:
        program.stdin.write(str(line)+nl)
    return program

def gnuplot_GifTest():
    commands = [\
        "set datafile separator ','",\
        "set terminal gif",\
        "set output",\
        "plot '-' using 1:2 with linespoints, '' using 1:2 with linespoints",\
        ]
    data = [\
        "1,1",\
        "2,2",\
        "3,5",\
        "4,2",\
        "5,1",\
        "e",\
        "1,5",\
        "2,4",\
        "3,1",\
        "4,4",\
        "5,5",\
        "e",\
        ]
    return (commands, data)

if __name__=="__main__":
    (commands, data) = gnuplot_GifTest()
    plotProg = gnuplot_ExecuteCommands(commands, data)
    (out, err) = (plotProg.stdout, plotProg.stderr)
    stdout.write(out.read())

That script dumps the graph to stdout as the last step in main. The equivalent command line (where the graph is piped to 'out.gif') would be:

gnuplot -e "set datafile separator ','; set terminal gif; set output; plot '-' using 1:2 with linespoints, '' using 1:2 with linespoints" > out.gif
1,1
2,2
3,5
4,2
5,1
e
1,5
2,4
3,1
4,4
5,5
e