[pygtk] Problem with pygtk, threads, an interactive interpreter and os.system()

Fernando Perez Fernando.Perez at colorado.edu
Wed Aug 18 01:06:34 WST 2004


Hi all,

I'm new to this list, but some of you in the python community may know me from 
ipython (http://ipython.scipy.org).  I'm trying to add gtk support to ipython, 
so that any gtk-based code can be executed and played with from an interactive 
shell.  Based on:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65109

I've written the attached mini-interpreter pyint-gtk.py, which runs without 
needing ipython to ease independent testing.  One of my main goals with this 
effort is to support the gtk and wx backends for matplotlib, but this should 
be useful to other users of pygtk as well.

The attached code works fairly well for most purposes, but I'm having problems 
with certain calls made by os.system(), specifically to gv (under Linux, 
Fedora Core 2 at the moment).  If I call os.system('gv foo.eps &'), gv seems 
to open fine, but after about 30 seconds of fiddling with it, especially if I 
open zoom sub-windows, the gv GUI just hangs.  The process becomes completely 
unresponsive, and the only way to kill it (and the gs children it spawns) is 
via a manual kill -9.  The weird thing is that I've tried opening other 
programs, including ggv on the same eps file (and xcalc, konqueror, etc), and 
nothing else seems to show this behavior.

But I'm very leery of releasing this code as production stuff (the version in 
ipython is different, since it integrates with the whole system, but the 
threading code is identical and shows the same problem).  I don't know for a 
fact that gv is the only culprit, and since I don't understand the root cause 
of the problem, I'm afraid of having ipython randomly lock up on people for no 
apparent reason.

I am a complete ignoramus on threading issues, and this code was blindly 
copied from the above recipe, so I may well be just doing something very 
stupid.  I would be very appreciative of any help on this.

Best to all,

Fernando Perez.
-------------- next part --------------
#!/usr/bin/env python
"""Multithreaded interactive interpreter with GTK and Matplotlib support.

Usage:

  pyint-gtk.py -> starts shell with gtk thread running separately

  pyint-gtk.py -mplot [filename] -> initializes matplotlib, optionally running
  the named file.  The shell starts after the file is executed.

Threading code inspired by:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65109, by Brian
McErlean and John Finlay.

Matplotlib support taken from interactive.py in the matplotlib distribution.

Also borrows liberally from code.py in the Python standard library."""

__author__ = "Fernando Perez <Fernando.Perez at colorado.edu>"

import sys
import code
import threading

import pygtk
pygtk.require("2.0")
import gtk

try:
    import readline
except ImportError:
    has_readline = False
else:
    has_readline = True

class MTConsole(code.InteractiveConsole):
    """Simple multi-threaded shell"""

    def __init__(self,on_kill=None,*args,**kw):
        code.InteractiveConsole.__init__(self,*args,**kw)
        self.code_to_run = None
        self.ready = threading.Condition()
        self._kill = False
        if on_kill is None:
            on_kill = []
        # Check that all things to kill are callable:
        for _ in on_kill:
            if not callable(_):
                raise TypeError,'on_kill must be a list of callables'
        self.on_kill = on_kill
        # Set up tab-completer
        if has_readline:
            import rlcompleter
            try:  # this form only works with python 2.3
                self.completer = rlcompleter.Completer(self.locals)
            except: # simpler for py2.2
                self.completer = rlcompleter.Completer()
                
            readline.set_completer(self.completer.complete)
            # Use tab for completions
            readline.parse_and_bind('tab: complete')
            # This forces readline to automatically print the above list when tab
            # completion is set to 'complete'.
            readline.parse_and_bind('set show-all-if-ambiguous on')
            # Bindings for incremental searches in the history. These searches
            # use the string typed so far on the command line and search
            # anything in the previous input history containing them.
            readline.parse_and_bind('"\C-r": reverse-search-history')
            readline.parse_and_bind('"\C-s": forward-search-history')

    def runsource(self, source, filename="<input>", symbol="single"):
        """Compile and run some source in the interpreter.

        Arguments are as for compile_command().

        One several things can happen:

        1) The input is incorrect; compile_command() raised an
        exception (SyntaxError or OverflowError).  A syntax traceback
        will be printed by calling the showsyntaxerror() method.

        2) The input is incomplete, and more input is required;
        compile_command() returned None.  Nothing happens.

        3) The input is complete; compile_command() returned a code
        object.  The code is executed by calling self.runcode() (which
        also handles run-time exceptions, except for SystemExit).

        The return value is True in case 2, False in the other cases (unless
        an exception is raised).  The return value can be used to
        decide whether to use sys.ps1 or sys.ps2 to prompt the next
        line.
        """
        try:
            code = self.compile(source, filename, symbol)
        except (OverflowError, SyntaxError, ValueError):
            # Case 1
            self.showsyntaxerror(filename)
            return False

        if code is None:
            # Case 2
            return True

        # Case 3
        # Store code in self, so the execution thread can handle it
        self.ready.acquire()
        self.code_to_run = code
        self.ready.wait()  # Wait until processed in timeout interval
        self.ready.release()

        return False

    def runcode(self):
        """Execute a code object.

        When an exception occurs, self.showtraceback() is called to display a
        traceback."""

        self.ready.acquire()
        if self._kill:
            print 'Closing threads...',
            sys.stdout.flush()
            for tokill in self.on_kill:
                tokill()
            print 'Done.'

        if self.code_to_run is not None:
            self.ready.notify()
            code.InteractiveConsole.runcode(self,self.code_to_run)

        self.code_to_run = None
        self.ready.release()
        return True

    def kill (self):
        """Kill the thread, returning when it has been shut down."""
        self.ready.acquire()
        self._kill = True
        self.ready.release()

class GTKInterpreter(threading.Thread):
    """Run a gtk mainloop() in a separate thread.
    Python commands can be passed to the thread where they will be executed.
    This is implemented by periodically checking for passed code using a
    GTK timeout callback.
    """
    TIMEOUT = 100 # Milisecond interval between timeouts.
    
    def __init__(self,banner=None):
        threading.Thread.__init__(self)
        self.banner = banner
        self.shell = MTConsole(on_kill=[gtk.mainquit])

    def run(self):
        gtk.timeout_add(self.TIMEOUT, self.shell.runcode)
        try:
            if gtk.gtk_version[0] >= 2:
                gtk.threads_init()
        except AttributeError:
            pass
        gtk.mainloop()

    def mainloop(self):
        self.start()
        self.pre_interact()
        self.shell.interact(self.banner)
        self.shell.kill()
        self.join()

    def pre_interact(self):
        """This method should be overridden by subclasses.

        It gets called right before interact(), but after the thread starts.
        Typically used to push initialization code into the interpreter"""
        
        pass

class MatplotLibInterpreter(GTKInterpreter):
    """Threaded interpreter with matplotlib support."""

    def __init__(self,banner=None):
        banner = """\nWelcome to matplotlib, a matlab-like python environment.
    help(matlab)   -> help on matlab compatible commands from matplotlib.
    help(plotting) -> help on plotting commands.
    """
        GTKInterpreter.__init__(self,banner)
        
    def pre_interact(self):
        """Initialize matplotlib before user interaction begins"""

        import matplotlib.matlab

        push = self.shell.push
        # Code to execute in user's namespace
        lines = ["import matplotlib",
                 "matplotlib.use('GTKAgg')",
                 "matplotlib.interactive(1)",
                 "import matplotlib.matlab as matlab",
                 "from matplotlib.matlab import *"]
        map(push,lines)

        # turn off rendering until end of script
        matplotlib.matlab.interactive = 0
        # Execute file if given.
        if len(sys.argv)>1:
            fname = sys.argv[1]
            try:
                inFile = file(fname, 'r')
            except IOError:
                print '*** ERROR *** Could not read file <%s>' % fname
            else:
                print '*** Executing file <%s>:' % fname
                for line in inFile:
                    if line.lstrip().find('show()')==0: continue
                    print '>>', line,
                    push(line)
                inFile.close()

if __name__ == '__main__':
    # Quick sys.argv hack to extract the option and leave filenames in sys.argv.
    # For real option handling, use optparse or getopt.
    if len(sys.argv) > 1 and sys.argv[1]=='-mplot':
        sys.argv = [sys.argv[0]]+sys.argv[2:]
        MatplotLibInterpreter().mainloop()
    else:
        GTKInterpreter().mainloop()


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