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

Here's a class that provides an interface to wgnuplot.exe:

from ctypes import *
import time
import sys
import os

#
# some win32 constants
#
WM_CHAR     = 0X0102
WM_CLOSE    = 16
SW_HIDE     = 0
STARTF_USESHOWWINDOW = 1

WORD    = c_ushort
DWORD   = c_ulong
LPBYTE  = POINTER(c_ubyte)
LPTSTR  = POINTER(c_char) 
HANDLE  = c_void_p

class STARTUPINFO(Structure):
    _fields_ = [("cb",DWORD),
        ("lpReserved",LPTSTR), 
        ("lpDesktop", LPTSTR),
        ("lpTitle", LPTSTR),
        ("dwX", DWORD),
        ("dwY", DWORD),
        ("dwXSize", DWORD),
        ("dwYSize", DWORD),
        ("dwXCountChars", DWORD),
        ("dwYCountChars", DWORD),
        ("dwFillAttribute", DWORD),
        ("dwFlags", DWORD),
        ("wShowWindow", WORD),
        ("cbReserved2", WORD),
        ("lpReserved2", LPBYTE),
        ("hStdInput", HANDLE),
        ("hStdOutput", HANDLE),
        ("hStdError", HANDLE),]

class PROCESS_INFORMATION(Structure):
    _fields_ = [("hProcess", HANDLE),
        ("hThread", HANDLE),
        ("dwProcessId", DWORD),
        ("dwThreadId", DWORD),]

#
# Gnuplot
#
class Gnuplot:
    #
    # __init__
    #
    def __init__(self, path_to_exe):
        # open gnuplot
        self.launch(path_to_exe)
        # wait till it's ready
        if(windll.user32.WaitForInputIdle(self.hProcess, 1000)):
            print "Error: Gnuplot timeout!"
            sys.exit(1)
        # get window handles
        self.hwndParent = windll.user32.FindWindowA(None, 'gnuplot')
        self.hwndText = windll.user32.FindWindowExA(self.hwndParent, None, 'wgnuplot_text', None)



    #
    # __del__
    #
    def __del__(self):
        windll.kernel32.CloseHandle(self.hProcess);
        windll.kernel32.CloseHandle(self.hThread);
        windll.user32.PostMessageA(self.hwndParent, WM_CLOSE, 0, 0)


    #
    # launch
    #
    def launch(self, path_to_exe):
        startupinfo = STARTUPINFO()
        process_information = PROCESS_INFORMATION()

        startupinfo.dwFlags = STARTF_USESHOWWINDOW
        startupinfo.wShowWindow = SW_HIDE

        if windll.kernel32.CreateProcessA(path_to_exe, None, None, None, False, 0, None, None, byref(startupinfo), byref(process_information)):
            self.hProcess = process_information.hProcess
            self.hThread = process_information.hThread
        else:
            print "Error: Create Process - Error code: ", windll.kernel32.GetLastError()
            sys.exit(1)



    #
    # execute
    #
    def execute(self, script, file_path):
        # make sure file doesn't exist
        try: os.unlink(file_path)
        except: pass

        # send script to gnuplot window
        for c in script: windll.user32.PostMessageA(self.hwndText, WM_CHAR, ord(c), 1L)

        # wait till gnuplot generates the chart
        while( not (os.path.exists(file_path) and (os.path.getsize(file_path) > 0))): time.sleep(0.01)