Added a first_reply signal to the heartbeat channel.

IPython/frontend/qt/kernelmanager.py

@@ -1,185 +1,202 b''
 """ Defines a KernelManager that provides signals and slots.
 """
 
 # System library imports.
 from PyQt4 import QtCore
-import zmq
 
 # IPython imports.
 from IPython.utils.traitlets import Type
 from IPython.zmq.kernelmanager import KernelManager, SubSocketChannel, \
     XReqSocketChannel, RepSocketChannel, HBSocketChannel
 from util import MetaQObjectHasTraits, SuperQObject
 
 
 class SocketChannelQObject(SuperQObject):
 
     # Emitted when the channel is started.
     started = QtCore.pyqtSignal()
 
     # Emitted when the channel is stopped.
     stopped = QtCore.pyqtSignal()
 
     #---------------------------------------------------------------------------
     # 'ZmqSocketChannel' interface
     #---------------------------------------------------------------------------
 
     def start(self):
         """ Reimplemented to emit signal.
         """
         super(SocketChannelQObject, self).start()
         self.started.emit()
 
     def stop(self):
         """ Reimplemented to emit signal.
         """
         super(SocketChannelQObject, self).stop()
         self.stopped.emit()
 
 
 class QtXReqSocketChannel(SocketChannelQObject, XReqSocketChannel):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
-    # Emitted when a reply has been received for the corresponding request type.
+    # Emitted when a reply has been received for the corresponding request
+    # type.
     execute_reply = QtCore.pyqtSignal(object)
     complete_reply = QtCore.pyqtSignal(object)
     object_info_reply = QtCore.pyqtSignal(object)
 
+    # Emitted when the first reply comes back
+    first_reply = QtCore.pyqtSignal(object)
+
+    # Used by the first_reply signal logic to determine if a reply is the 
+    # first.
+    _handlers_called = False
+
     #---------------------------------------------------------------------------
     # 'XReqSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         signal = getattr(self, msg_type, None)
         if signal:
             signal.emit(msg)
 
+        if not self._handlers_called:
+            self.first_reply.emit()
+
+        self._handlers_called = True
+
+    def reset_first_reply(self):
+        """ Reset the first_reply signal to fire again on the next reply.
+        """
+        self._handlers_called = False
+
 
 class QtSubSocketChannel(SocketChannelQObject, SubSocketChannel):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'stream' is received.
     stream_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyin' is received.
     pyin_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyout' is received.
     pyout_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyerr' is received.
     pyerr_received = QtCore.pyqtSignal(object)
 
     # Emitted when a crash report message is received from the kernel's
     # last-resort sys.excepthook.
     crash_received = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'SubSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         signal = getattr(self, msg_type + '_received', None)
         if signal:
             signal.emit(msg)
         elif msg_type in ('stdout', 'stderr'):
             self.stream_received.emit(msg)
 
     def flush(self):
         """ Reimplemented to ensure that signals are dispatched immediately.
         """
         super(QtSubSocketChannel, self).flush()
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtRepSocketChannel(SocketChannelQObject, RepSocketChannel):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when an input request is received.
     input_requested = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'RepSocketChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         if msg_type == 'input_request':
             self.input_requested.emit(msg)
 
 
 class QtHBSocketChannel(SocketChannelQObject, HBSocketChannel):
 
     # Emitted when the kernel has died.
     kernel_died = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'HBSocketChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, since_last_heartbeat):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.kernel_died.emit(since_last_heartbeat)
 
 
 class QtKernelManager(KernelManager, SuperQObject):
     """ A KernelManager that provides signals and slots.
     """
 
     __metaclass__ = MetaQObjectHasTraits
 
     # Emitted when the kernel manager has started listening.
     started_channels = QtCore.pyqtSignal()
 
     # Emitted when the kernel manager has stopped listening.
     stopped_channels = QtCore.pyqtSignal()
 
     # Use Qt-specific channel classes that emit signals.
     sub_channel_class = Type(QtSubSocketChannel)
     xreq_channel_class = Type(QtXReqSocketChannel)
     rep_channel_class = Type(QtRepSocketChannel)
     hb_channel_class = Type(QtHBSocketChannel)
 
     #---------------------------------------------------------------------------
     # 'KernelManager' interface
     #---------------------------------------------------------------------------
     
     def start_channels(self, *args, **kw):
         """ Reimplemented to emit signal.
         """
         super(QtKernelManager, self).start_channels(*args, **kw)
         self.started_channels.emit()
 
     def stop_channels(self):
         """ Reimplemented to emit signal.
         """ 
         super(QtKernelManager, self).stop_channels()
         self.stopped_channels.emit()

IPython/zmq/ipkernel.py

@@ -1,612 +1,612 b''
 #!/usr/bin/env python
 """A simple interactive kernel that talks to a frontend over 0MQ.
 
 Things to do:
 
 * Implement `set_parent` logic. Right before doing exec, the Kernel should
   call set_parent on all the PUB objects with the message about to be executed.
 * Implement random port and security key logic.
 * Implement control messages.
 * Implement event loop and poll version.
 """
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 # Standard library imports.
 import __builtin__
 import atexit
 import sys
 import time
 import traceback
 
 # System library imports.
 import zmq
 
 # Local imports.
 from IPython.config.configurable import Configurable
 from IPython.utils import io
 from IPython.utils.jsonutil import json_clean
 from IPython.lib import pylabtools
 from IPython.utils.traitlets import Instance, Float
 from entry_point import (base_launch_kernel, make_argument_parser, make_kernel,
                          start_kernel)
 from iostream import OutStream
 from session import Session, Message
 from zmqshell import ZMQInteractiveShell
 
 #-----------------------------------------------------------------------------
 # Main kernel class
 #-----------------------------------------------------------------------------
 
 class Kernel(Configurable):
 
     #---------------------------------------------------------------------------
     # Kernel interface
     #---------------------------------------------------------------------------
 
     shell = Instance('IPython.core.interactiveshell.InteractiveShellABC')
     session = Instance(Session)
     reply_socket = Instance('zmq.Socket')
     pub_socket = Instance('zmq.Socket')
     req_socket = Instance('zmq.Socket')
 
     # Private interface
 
     # Time to sleep after flushing the stdout/err buffers in each execute
     # cycle.  While this introduces a hard limit on the minimal latency of the
     # execute cycle, it helps prevent output synchronization problems for
     # clients.
     # Units are in seconds.  The minimum zmq latency on local host is probably
     # ~150 microseconds, set this to 500us for now.  We may need to increase it
     # a little if it's not enough after more interactive testing.
     _execute_sleep = Float(0.0005, config=True)
 
     # Frequency of the kernel's event loop.
     # Units are in seconds, kernel subclasses for GUI toolkits may need to
     # adapt to milliseconds.
     _poll_interval = Float(0.05, config=True)
 
     # If the shutdown was requested over the network, we leave here the
     # necessary reply message so it can be sent by our registered atexit
     # handler.  This ensures that the reply is only sent to clients truly at
     # the end of our shutdown process (which happens after the underlying
     # IPython shell's own shutdown).
     _shutdown_message = None
 
     # This is a dict of port number that the kernel is listening on. It is set
     # by record_ports and used by connect_request.
     _recorded_ports = None
     
     def __init__(self, **kwargs):
         super(Kernel, self).__init__(**kwargs)
 
         # Before we even start up the shell, register *first* our exit handlers
         # so they come before the shell's
         atexit.register(self._at_shutdown)
 
         # Initialize the InteractiveShell subclass
         self.shell = ZMQInteractiveShell.instance()
         self.shell.displayhook.session = self.session
         self.shell.displayhook.pub_socket = self.pub_socket
 
         # TMP - hack while developing
         self.shell._reply_content = None
 
         # Build dict of handlers for message types
         msg_types = [ 'execute_request', 'complete_request', 
                       'object_info_request', 'history_request',
-                      'shutdown_request']
+                      'connect_request', 'shutdown_request']
         self.handlers = {}
         for msg_type in msg_types:
             self.handlers[msg_type] = getattr(self, msg_type)
 
     def do_one_iteration(self):
         """Do one iteration of the kernel's evaluation loop.
         """
         try:
             ident = self.reply_socket.recv(zmq.NOBLOCK)
         except zmq.ZMQError, e:
             if e.errno == zmq.EAGAIN:
                 return
             else:
                 raise
         # FIXME: Bug in pyzmq/zmq?
         # assert self.reply_socket.rcvmore(), "Missing message part."
         msg = self.reply_socket.recv_json()
         
         # Print some info about this message and leave a '--->' marker, so it's
         # easier to trace visually the message chain when debugging.  Each
         # handler prints its message at the end.
         # Eventually we'll move these from stdout to a logger.
         io.raw_print('\n*** MESSAGE TYPE:', msg['msg_type'], '***')
         io.raw_print('   Content: ', msg['content'],
                      '\n   --->\n   ', sep='', end='')
 
         # Find and call actual handler for message
         handler = self.handlers.get(msg['msg_type'], None)
         if handler is None:
             io.raw_print_err("UNKNOWN MESSAGE TYPE:", msg)
         else:
             handler(ident, msg)
             
         # Check whether we should exit, in case the incoming message set the
         # exit flag on
         if self.shell.exit_now:
             io.raw_print('\nExiting IPython kernel...')
             # We do a normal, clean exit, which allows any actions registered
             # via atexit (such as history saving) to take place.
             sys.exit(0)
 
 
     def start(self):
         """ Start the kernel main loop.
         """
         while True:
             time.sleep(self._poll_interval)
             self.do_one_iteration()
 
     def record_ports(self, xrep_port, pub_port, req_port, hb_port):
         """Record the ports that this kernel is using.
 
         The creator of the Kernel instance must call this methods if they
         want the :meth:`connect_request` method to return the port numbers.
         """
         self._recorded_ports = {
             'xrep_port' : xrep_port,
             'pub_port' : pub_port,
             'req_port' : req_port,
             'hb_port' : hb_port
         }
 
     #---------------------------------------------------------------------------
     # Kernel request handlers
     #---------------------------------------------------------------------------
 
     def _publish_pyin(self, code, parent):
         """Publish the code request on the pyin stream."""
 
         pyin_msg = self.session.msg(u'pyin',{u'code':code}, parent=parent)
         self.pub_socket.send_json(pyin_msg)
 
     def execute_request(self, ident, parent):
         try:
             content = parent[u'content']
             code = content[u'code']
             silent = content[u'silent'] 
         except:
             io.raw_print_err("Got bad msg: ")
             io.raw_print_err(Message(parent))
             return
 
         shell = self.shell # we'll need this a lot here
 
         # Replace raw_input. Note that is not sufficient to replace 
         # raw_input in the user namespace.
         raw_input = lambda prompt='': self._raw_input(prompt, ident, parent)
         __builtin__.raw_input = raw_input
 
         # Set the parent message of the display hook and out streams.
         shell.displayhook.set_parent(parent)
         sys.stdout.set_parent(parent)
         sys.stderr.set_parent(parent)
 
         # Re-broadcast our input for the benefit of listening clients, and
         # start computing output
         if not silent:
             self._publish_pyin(code, parent)
 
         reply_content = {}
         try:
             if silent:
                 # runcode uses 'exec' mode, so no displayhook will fire, and it
                 # doesn't call logging or history manipulations.  Print
                 # statements in that code will obviously still execute.
                 shell.runcode(code)
             else:
                 # FIXME: runlines calls the exception handler itself.
                 shell._reply_content = None
 
                 # For now leave this here until we're sure we can stop using it
                 #shell.runlines(code)
 
                 # Experimental: cell mode!  Test more before turning into
                 # default and removing the hacks around runlines.
                 shell.run_cell(code)
         except:
             status = u'error'
             # FIXME: this code right now isn't being used yet by default,
             # because the runlines() call above directly fires off exception
             # reporting.  This code, therefore, is only active in the scenario
             # where runlines itself has an unhandled exception.  We need to
             # uniformize this, for all exception construction to come from a
             # single location in the codbase.
             etype, evalue, tb = sys.exc_info()
             tb_list = traceback.format_exception(etype, evalue, tb)
             reply_content.update(shell._showtraceback(etype, evalue, tb_list))
         else:
             status = u'ok'
 
         reply_content[u'status'] = status
         # Compute the execution counter so clients can display prompts
         reply_content['execution_count'] = shell.displayhook.prompt_count
 
         # FIXME - fish exception info out of shell, possibly left there by
         # runlines.  We'll need to clean up this logic later.
         if shell._reply_content is not None:
             reply_content.update(shell._reply_content)
 
         # At this point, we can tell whether the main code execution succeeded
         # or not.  If it did, we proceed to evaluate user_variables/expressions
         if reply_content['status'] == 'ok':
             reply_content[u'user_variables'] = \
                          shell.get_user_variables(content[u'user_variables'])
             reply_content[u'user_expressions'] = \
                          shell.eval_expressions(content[u'user_expressions'])
         else:
             # If there was an error, don't even try to compute variables or
             # expressions
             reply_content[u'user_variables'] = {}
             reply_content[u'user_expressions'] = {}
 
         # Payloads should be retrieved regardless of outcome, so we can both
         # recover partial output (that could have been generated early in a
         # block, before an error) and clear the payload system always.
         reply_content[u'payload'] = shell.payload_manager.read_payload()
         # Be agressive about clearing the payload because we don't want
         # it to sit in memory until the next execute_request comes in.
         shell.payload_manager.clear_payload()
 
         # Send the reply.
         reply_msg = self.session.msg(u'execute_reply', reply_content, parent)
         io.raw_print(reply_msg)
 
         # Flush output before sending the reply.
         sys.stdout.flush()
         sys.stderr.flush()
         # FIXME: on rare occasions, the flush doesn't seem to make it to the
         # clients... This seems to mitigate the problem, but we definitely need
         # to better understand what's going on.
         if self._execute_sleep:
             time.sleep(self._execute_sleep)
         
         self.reply_socket.send(ident, zmq.SNDMORE)
         self.reply_socket.send_json(reply_msg)
         if reply_msg['content']['status'] == u'error':
             self._abort_queue()
 
     def complete_request(self, ident, parent):
         txt, matches = self._complete(parent)
         matches = {'matches' : matches,
                    'matched_text' : txt,
                    'status' : 'ok'}
         completion_msg = self.session.send(self.reply_socket, 'complete_reply',
                                            matches, parent, ident)
         io.raw_print(completion_msg)
 
     def object_info_request(self, ident, parent):
         object_info = self.shell.object_inspect(parent['content']['oname'])
         # Before we send this object over, we turn it into a dict and we scrub
         # it for JSON usage
         oinfo = json_clean(object_info._asdict())
         msg = self.session.send(self.reply_socket, 'object_info_reply',
                                 oinfo, parent, ident)
         io.raw_print(msg)
 
     def history_request(self, ident, parent):
         output = parent['content']['output']
         index = parent['content']['index']
         raw = parent['content']['raw']
         hist = self.shell.get_history(index=index, raw=raw, output=output)
         content = {'history' : hist}
         msg = self.session.send(self.reply_socket, 'history_reply',
                                 content, parent, ident)
         io.raw_print(msg)
 
     def connect_request(self, ident, parent):
         if self._recorded_ports is not None:
             content = self._recorded_ports.copy()
         else:
             content = {}
         msg = self.session.send(self.reply_socket, 'connect_reply',
                                 content, parent, ident)
         io.raw_print(msg)
 
     def shutdown_request(self, ident, parent):
         self.shell.exit_now = True
         self._shutdown_message = self.session.msg(u'shutdown_reply', {}, parent)
         sys.exit(0)
 
     #---------------------------------------------------------------------------
     # Protected interface
     #---------------------------------------------------------------------------
 
     def _abort_queue(self):
         while True:
             try:
                 ident = self.reply_socket.recv(zmq.NOBLOCK)
             except zmq.ZMQError, e:
                 if e.errno == zmq.EAGAIN:
                     break
             else:
                 assert self.reply_socket.rcvmore(), \
                        "Unexpected missing message part."
                 msg = self.reply_socket.recv_json()
             io.raw_print("Aborting:\n", Message(msg))
             msg_type = msg['msg_type']
             reply_type = msg_type.split('_')[0] + '_reply'
             reply_msg = self.session.msg(reply_type, {'status' : 'aborted'}, msg)
             io.raw_print(reply_msg)
             self.reply_socket.send(ident,zmq.SNDMORE)
             self.reply_socket.send_json(reply_msg)
             # We need to wait a bit for requests to come in. This can probably
             # be set shorter for true asynchronous clients.
             time.sleep(0.1)
 
     def _raw_input(self, prompt, ident, parent):
         # Flush output before making the request.
         sys.stderr.flush()
         sys.stdout.flush()
 
         # Send the input request.
         content = dict(prompt=prompt)
         msg = self.session.msg(u'input_request', content, parent)
         self.req_socket.send_json(msg)
 
         # Await a response.
         reply = self.req_socket.recv_json()
         try:
             value = reply['content']['value']
         except:
             io.raw_print_err("Got bad raw_input reply: ")
             io.raw_print_err(Message(parent))
             value = ''
         return value
     
     def _complete(self, msg):
         c = msg['content']
         try:
             cpos = int(c['cursor_pos'])
         except:
             # If we don't get something that we can convert to an integer, at
             # least attempt the completion guessing the cursor is at the end of
             # the text, if there's any, and otherwise of the line
             cpos = len(c['text'])
             if cpos==0:
                 cpos = len(c['line'])
         return self.shell.complete(c['text'], c['line'], cpos)
 
     def _object_info(self, context):
         symbol, leftover = self._symbol_from_context(context)
         if symbol is not None and not leftover:
             doc = getattr(symbol, '__doc__', '')
         else:
             doc = ''
         object_info = dict(docstring = doc)
         return object_info
 
     def _symbol_from_context(self, context):
         if not context:
             return None, context
 
         base_symbol_string = context[0]
         symbol = self.shell.user_ns.get(base_symbol_string, None)
         if symbol is None:
             symbol = __builtin__.__dict__.get(base_symbol_string, None)
         if symbol is None:
             return None, context
 
         context = context[1:]
         for i, name in enumerate(context):
             new_symbol = getattr(symbol, name, None)
             if new_symbol is None:
                 return symbol, context[i:]
             else:
                 symbol = new_symbol
 
         return symbol, []
 
     def _at_shutdown(self):
         """Actions taken at shutdown by the kernel, called by python's atexit.
         """
         # io.rprint("Kernel at_shutdown") # dbg
         if self._shutdown_message is not None:
             self.reply_socket.send_json(self._shutdown_message)
             io.raw_print(self._shutdown_message)
             # A very short sleep to give zmq time to flush its message buffers
             # before Python truly shuts down.
             time.sleep(0.01)
 
 
 class QtKernel(Kernel):
     """A Kernel subclass with Qt support."""
 
     def start(self):
         """Start a kernel with QtPy4 event loop integration."""
 
         from PyQt4 import QtCore
         from IPython.lib.guisupport import get_app_qt4, start_event_loop_qt4
 
         self.app = get_app_qt4([" "])
         self.app.setQuitOnLastWindowClosed(False)
         self.timer = QtCore.QTimer()
         self.timer.timeout.connect(self.do_one_iteration)
         # Units for the timer are in milliseconds
         self.timer.start(1000*self._poll_interval)
         start_event_loop_qt4(self.app)
 
 
 class WxKernel(Kernel):
     """A Kernel subclass with Wx support."""
 
     def start(self):
         """Start a kernel with wx event loop support."""
 
         import wx
         from IPython.lib.guisupport import start_event_loop_wx
 
         doi = self.do_one_iteration
          # Wx uses milliseconds
         poll_interval = int(1000*self._poll_interval)
 
         # We have to put the wx.Timer in a wx.Frame for it to fire properly.
         # We make the Frame hidden when we create it in the main app below.
         class TimerFrame(wx.Frame):
             def __init__(self, func):
                 wx.Frame.__init__(self, None, -1)
                 self.timer = wx.Timer(self)
                 # Units for the timer are in milliseconds
                 self.timer.Start(poll_interval)
                 self.Bind(wx.EVT_TIMER, self.on_timer)
                 self.func = func
 
             def on_timer(self, event):
                 self.func()
 
         # We need a custom wx.App to create our Frame subclass that has the
         # wx.Timer to drive the ZMQ event loop.
         class IPWxApp(wx.App):
             def OnInit(self):
                 self.frame = TimerFrame(doi)
                 self.frame.Show(False)
                 return True
 
         # The redirect=False here makes sure that wx doesn't replace
         # sys.stdout/stderr with its own classes.
         self.app = IPWxApp(redirect=False)
         start_event_loop_wx(self.app)
 
 
 class TkKernel(Kernel):
     """A Kernel subclass with Tk support."""
 
     def start(self):
         """Start a Tk enabled event loop."""
 
         import Tkinter
         doi = self.do_one_iteration
         # Tk uses milliseconds
         poll_interval = int(1000*self._poll_interval)
         # For Tkinter, we create a Tk object and call its withdraw method.
         class Timer(object):
             def __init__(self, func):
                 self.app = Tkinter.Tk()
                 self.app.withdraw()
                 self.func = func
                 
             def on_timer(self):
                 self.func()
                 self.app.after(poll_interval, self.on_timer)
                 
             def start(self):
                 self.on_timer()  # Call it once to get things going.
                 self.app.mainloop()
 
         self.timer = Timer(doi)
         self.timer.start()
 
 
 class GTKKernel(Kernel):
     """A Kernel subclass with GTK support."""
     
     def start(self):
         """Start the kernel, coordinating with the GTK event loop"""
         from .gui.gtkembed import GTKEmbed
         
         gtk_kernel = GTKEmbed(self)
         gtk_kernel.start()
 
 
 #-----------------------------------------------------------------------------
 # Kernel main and launch functions
 #-----------------------------------------------------------------------------
 
 def launch_kernel(xrep_port=0, pub_port=0, req_port=0, hb_port=0,
                   independent=False, pylab=False):
     """Launches a localhost kernel, binding to the specified ports.
 
     Parameters
     ----------
     xrep_port : int, optional
         The port to use for XREP channel.
 
     pub_port : int, optional
         The port to use for the SUB channel.
 
     req_port : int, optional
         The port to use for the REQ (raw input) channel.
 
     hb_port : int, optional
         The port to use for the hearbeat REP channel.
 
     independent : bool, optional (default False) 
         If set, the kernel process is guaranteed to survive if this process
         dies. If not set, an effort is made to ensure that the kernel is killed
         when this process dies. Note that in this case it is still good practice
         to kill kernels manually before exiting.
 
     pylab : bool or string, optional (default False)
         If not False, the kernel will be launched with pylab enabled. If a
         string is passed, matplotlib will use the specified backend. Otherwise,
         matplotlib's default backend will be used.
 
     Returns
     -------
     A tuple of form:
         (kernel_process, xrep_port, pub_port, req_port)
     where kernel_process is a Popen object and the ports are integers.
     """
     extra_arguments = []
     if pylab:
         extra_arguments.append('--pylab')
         if isinstance(pylab, basestring):
             extra_arguments.append(pylab)
     return base_launch_kernel('from IPython.zmq.ipkernel import main; main()',
                               xrep_port, pub_port, req_port, hb_port, 
                               independent, extra_arguments)
 
 
 def main():
     """ The IPython kernel main entry point.
     """
     parser = make_argument_parser()
     parser.add_argument('--pylab', type=str, metavar='GUI', nargs='?', 
                         const='auto', help = \
 "Pre-load matplotlib and numpy for interactive use. If GUI is not \
 given, the GUI backend is matplotlib's, otherwise use one of: \
 ['tk', 'gtk', 'qt', 'wx', 'inline'].")
     namespace = parser.parse_args()
 
     kernel_class = Kernel
 
     kernel_classes = {
         'qt' : QtKernel,
         'qt4': QtKernel,
         'inline': Kernel,
         'wx' : WxKernel,
         'tk' : TkKernel,
         'gtk': GTKKernel,
     }
     if namespace.pylab:
         if namespace.pylab == 'auto':
             gui, backend = pylabtools.find_gui_and_backend()
         else:
             gui, backend = pylabtools.find_gui_and_backend(namespace.pylab)
         kernel_class = kernel_classes.get(gui)
         if kernel_class is None:
             raise ValueError('GUI is not supported: %r' % gui)
         pylabtools.activate_matplotlib(backend)
 
     kernel = make_kernel(namespace, kernel_class, OutStream)
 
     if namespace.pylab:
         pylabtools.import_pylab(kernel.shell.user_ns, backend,
                                 shell=kernel.shell)
 
     start_kernel(namespace, kernel)
 
 
 if __name__ == '__main__':
     main()