gnuplot-py-users Mailing List for Gnuplot.py

Hi,

the problem is described in the FAQ of the gnuplot-package.

(You will get the same problem if you use Gnuplot in function which returns 
before gnuplot is finished, for example:

def makeimage(data, file):
	g=Gnuplot.Gnuplot()
	g('set term png')
	g('set output \'' + file+ '\'')
	g.plot(data)
	return

you will get something like this:

    gnuplot> plot  '/tmp/@24463.2'
                   ^
             can't read data file "/tmp/@24463.2"
             line 0: (No such file or directory)
)

A possible fix would be to use popen2(available on unix and windows)  instead 
of os.popen and to define __del__(self) to savely shutdown the gnuplot 
process.

the last part of my gp_unix.py looks like this:


#from os import popen
from popen2 import Popen3

def test_persist():
    """Determine whether gnuplot recognizes the option '-persist'.

    If the configuration variable 'recognizes_persist' is set (i.e.,
    to something other than 'None'), return that value.  Otherwise,
    try to determine whether the installed version of gnuplot
    recognizes the -persist option.  (If it doesn't, it should emit an
    error message with '-persist' in the first line.)  Then set
    'recognizes_persist' accordingly for future reference.

    """

    if GnuplotOpts.recognizes_persist is None:
        import string
        g = Popen3('echo | %s -persist 2>&1' % GnuplotOpts.gnuplot_command, 
'r')
        response = g.readlines()
        g.close()
        GnuplotOpts.recognizes_persist = (
            (not response) or (string.find(response[0], '-persist') == -1))
    return GnuplotOpts.recognizes_persist


class GnuplotProcess:
    """Unsophisticated interface to a running gnuplot program.

    This represents a running gnuplot program and the means to
    communicate with it at a primitive level (i.e., pass it commands
    or data).  When the object is destroyed, the gnuplot program exits
    (unless the 'persist' option was set).  The communication is
    one-way; gnuplot's text output just goes to stdout with no attempt
    to check it for error messages.

    Members:

        'gnuplot' -- the pipe to the gnuplot command.

    Methods:

        '__init__' -- start up the program.

        '__call__' -- pass an arbitrary string to the gnuplot program,
            followed by a newline.

        'write' -- pass an arbitrary string to the gnuplot program.

        'flush' -- cause pending output to be written immediately.

    """

    def __init__(self, persist=None):
        """Start a gnuplot process.

        Create a 'GnuplotProcess' object.  This starts a gnuplot
        program and prepares to write commands to it.

        Keyword arguments:

          'persist=1' -- start gnuplot with the '-persist' option,
              (which leaves the plot window on the screen even after
              the gnuplot program ends, and creates a new plot window
              each time the terminal type is set to 'x11').  This
              option is not available on older versions of gnuplot.

        """

        if persist is None:
            persist = GnuplotOpts.prefer_persist
        if persist:
            if not test_persist():
                raise ('-persist does not seem to be supported '
                       'by your version of gnuplot!')
            self.gnuplot = Popen3('%s -persist' % GnuplotOpts.gnuplot_command,
                                 'w')
        else:
            self.gnuplot = Popen3(GnuplotOpts.gnuplot_command, 'w')
	
	
        # forward write and flush methods:
        self.write = self.gnuplot.tochild.write
        self.flush = self.gnuplot.tochild.flush

    def __call__(self, s):
        """Send a command string to gnuplot, followed by newline."""

        self.write(s + '\n')
        self.flush()
    def __del__(self):
	self.write('exit\n')
	self.flush()
	self.gnuplot.wait()
	
Regards,

Hendrik Muhs
P.S. for answers: Please CC me, because I am not subscribed to this list