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gp_unix.py
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gp_unix.py
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# $Id: gp_unix.py 292 2006-03-03 09:49:04Z mhagger $
# Copyright (C) 1998-2003 Michael Haggerty <mhagger@alum.mit.edu>
#
# This file is licensed under the GNU Lesser General Public License
# (LGPL). See LICENSE.txt for details.
"""gp_unix -- an interface to gnuplot used for unix platforms.
This file implements a low-level interface to a gnuplot program for a
unix platform (actually it is used for any non-Windows, non-Mac
system). This file should be imported through gp.py, which in turn
should be imported via 'import Gnuplot' rather than these low-level
interfaces.
"""
# ############ Configuration variables: ################################
class GnuplotOpts:
"""The configuration options for gnuplot on generic platforms.
Store the options in a class to make them easy to import and
modify en masse. If you want to modify the options from the
command line or within a running program, do something like the
following::
import Gnuplot
Gnuplot.GnuplotOpts.gnuplot_command = '/bin/mygnuplot'
"""
# Command to start up the gnuplot program. If your version of
# gnuplot is run otherwise, specify the correct command here. You
# could also specify a full path or append command-line options
# here if you wish.
gnuplot_command = 'gnuplot'
# Recent versions of gnuplot (at least for Xwindows) allow a
# `-persist' command-line option when starting up gnuplot. When
# this option is specified, graph windows remain on the screen
# even after you quit gnuplot (type `q' in the window to close
# it). This can be handy but unfortunately it is not supported by
# older versions of gnuplot. The following configuration variable
# specifies whether the user's version of gnuplot recognizes this
# option or not. You can set this variable to 1 (supports
# -persist) or 0 (doesn't support) yourself; if you leave it with
# the value None then the first time you create a Gnuplot object
# it will try to detect automatically whether your version accepts
# this option.
recognizes_persist = None # test automatically on first use
# What should be the default if the persist option is not
# specified explicitly?
prefer_persist = 0
# Recent versions of gnuplot allow you to specify a `binary'
# option to the splot command for grid data, which means that the
# data file is to be read in binary format. This option saves
# substantial time writing and reading the file, and can also save
# substantial disk space and therefore it is the default for that
# type of plot. But if you have an older version of gnuplot (or
# you prefer text format) you can disable the binary option in
# either of two ways: (a) set the following variable to 0; or (b)
# pass `binary=0' to the GridData constructor. (Note that the
# demo uses binary=0 to maximize portability.)
recognizes_binary_splot = 1
# Data can be passed to gnuplot through a temporary file or as
# inline data (i.e., the filename is set to '-' and the data is
# entered into the gnuplot interpreter followed by 'e'). If
# prefer_inline_data is true, then use the inline method as
# default whenever it is supported. This should be fast but will
# use more memory since currently the inline data is put into a
# big string when the PlotItem is created.
prefer_inline_data = 0
# Does Python implement the threading module and os.mkfifo on this
# operating system? If so, the _FIFOFileItem class will be
# defined in PlotItem.py.
support_fifo = 1
# Should FIFOs be used to send data to gnuplot by default?
prefer_fifo_data = 1
# After a hardcopy is produced, we have to set the terminal type
# back to `on screen' using gnuplot's `set terminal' command. The
# following is the usual setting for Xwindows. If it is wrong,
# change the following line to select the terminal type you prefer
# to use for on-screen work.
default_term = 'x11'
# Gnuplot can plot to a printer by using "set output '| ...'"
# where ... is the name of a program that sends its stdin to a
# printer, or by "set output 'printer_device', where
# 'printer_device is the name of a file-like interface to the
# printer. On my machine the appropriate program is `lpr', as set
# below. On your computer it may be something different (like
# `lp'); you can set that by changing the variable below. You can
# also add options to the print command if needed.
default_lpr = '| lpr'
# Enhanced postscript is an option to the postscript terminal
# driver that requests enhanced treatment of strings (for example,
# font changes, superscripts, and subscripts). Set to 1 to enable
# or 0 to disable. If you have a version of gnuplot earlier than
# 3.7, you should set this to None (*not* 0!) so that the option
# is not used at all.
prefer_enhanced_postscript = 1
# ############ End of configuration options ############################
from os import popen
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 = popen('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.
'close' -- close the connection to gnuplot.
"""
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 Exception('-persist does not seem to be supported '
'by your version of gnuplot!')
self.gnuplot = popen('%s -persist' % GnuplotOpts.gnuplot_command,
'w')
else:
self.gnuplot = popen(GnuplotOpts.gnuplot_command, 'w')
# forward write and flush methods:
self.write = self.gnuplot.write
self.flush = self.gnuplot.flush
def close(self):
if self.gnuplot is not None:
self.gnuplot.close()
self.gnuplot = None
def __del__(self):
self.close()
def __call__(self, s):
"""Send a command string to gnuplot, followed by newline."""
self.write(s + '\n')
self.flush()