* Change input mechanism: replace raw_input instead of stdin.

* Made 'kernel' a public attribute of KernelManager.

IPython/frontend/qt/console/frontend_widget.py

@@ -1,382 +1,382
 # Standard library imports
 import signal
 import sys
 
 # System library imports
 from pygments.lexers import PythonLexer
 from PyQt4 import QtCore, QtGui
 import zmq
 
 # Local imports
 from IPython.core.inputsplitter import InputSplitter
 from call_tip_widget import CallTipWidget
 from completion_lexer import CompletionLexer
 from console_widget import HistoryConsoleWidget
 from pygments_highlighter import PygmentsHighlighter
 
 
 class FrontendHighlighter(PygmentsHighlighter):
     """ A PygmentsHighlighter that can be turned on and off and that ignores
         prompts.
     """
 
     def __init__(self, frontend):
         super(FrontendHighlighter, self).__init__(frontend.document())
         self._current_offset = 0
         self._frontend = frontend
         self.highlighting_on = False
 
     def highlightBlock(self, qstring):
         """ Highlight a block of text. Reimplemented to highlight selectively.
         """
         if not self.highlighting_on:
             return
 
         # The input to this function is unicode string that may contain
         # paragraph break characters, non-breaking spaces, etc. Here we acquire
         # the string as plain text so we can compare it.
         current_block = self.currentBlock()
         string = self._frontend._get_block_plain_text(current_block)
 
         # Decide whether to check for the regular or continuation prompt.
         if current_block.contains(self._frontend._prompt_pos):
             prompt = self._frontend._prompt
         else:
             prompt = self._frontend._continuation_prompt
 
         # Don't highlight the part of the string that contains the prompt.
         if string.startswith(prompt):
             self._current_offset = len(prompt)
             qstring.remove(0, len(prompt))
         else:
             self._current_offset = 0
 
         PygmentsHighlighter.highlightBlock(self, qstring)
 
     def setFormat(self, start, count, format):
         """ Reimplemented to highlight selectively.
         """
         start += self._current_offset
         PygmentsHighlighter.setFormat(self, start, count, format)
 
 
 class FrontendWidget(HistoryConsoleWidget):
     """ A Qt frontend for a generic Python kernel.
     """
    
     # Emitted when an 'execute_reply' is received from the kernel.
     executed = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'QObject' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, parent=None):
         super(FrontendWidget, self).__init__(parent)
 
         # FrontendWidget protected variables.
         self._call_tip_widget = CallTipWidget(self)
         self._completion_lexer = CompletionLexer(PythonLexer())
         self._hidden = True
         self._highlighter = FrontendHighlighter(self)
         self._input_splitter = InputSplitter(input_mode='replace')
         self._kernel_manager = None
 
         # Configure the ConsoleWidget.
         self.tab_width = 4
         self._set_continuation_prompt('... ')
 
         self.document().contentsChange.connect(self._document_contents_change)
 
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
 
     def focusOutEvent(self, event):
         """ Reimplemented to hide calltips.
         """
         self._call_tip_widget.hide()
         super(FrontendWidget, self).focusOutEvent(event)
 
     def keyPressEvent(self, event):
         """ Reimplemented to allow calltips to process events and to send
             signals to the kernel.
         """
         if self._executing and event.key() == QtCore.Qt.Key_C and \
                 self._control_down(event.modifiers()):
             self._interrupt_kernel()
         else:
             if self._call_tip_widget.isVisible():
                 self._call_tip_widget.keyPressEvent(event)
             super(FrontendWidget, self).keyPressEvent(event)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _is_complete(self, source, interactive):
         """ Returns whether 'source' can be completely processed and a new
             prompt created. When triggered by an Enter/Return key press,
             'interactive' is True; otherwise, it is False.
         """
         complete = self._input_splitter.push(source.expandtabs(4))
         if interactive:
             complete = not self._input_splitter.push_accepts_more()
         return complete
 
     def _execute(self, source, hidden):
         """ Execute 'source'. If 'hidden', do not show any output.
         """
         self.kernel_manager.xreq_channel.execute(source)
         self._hidden = hidden
         
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
         if not self._reading:
             self._highlighter.highlighting_on = True
 
             # Auto-indent if this is a continuation prompt.
             if self._get_prompt_cursor().blockNumber() != \
                     self._get_end_cursor().blockNumber():
                 spaces = self._input_splitter.indent_spaces
                 self.appendPlainText('\t' * (spaces / self.tab_width))
                 self.appendPlainText(' ' * (spaces % self.tab_width))
 
     def _prompt_finished_hook(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         if not self._reading:
             self._highlighter.highlighting_on = False
 
     def _tab_pressed(self):
         """ Called when the tab key is pressed. Returns whether to continue
             processing the event.
         """
         self._keep_cursor_in_buffer()
         cursor = self.textCursor()
         return not self._complete()
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' interface
     #---------------------------------------------------------------------------
 
     def execute_file(self, path, hidden=False):
         """ Attempts to execute file with 'path'. If 'hidden', no output is
             shown.
         """
         self.execute('execfile("%s")' % path, hidden=hidden)
 
     def _get_kernel_manager(self):
         """ Returns the current kernel manager.
         """
         return self._kernel_manager
 
     def _set_kernel_manager(self, kernel_manager):
         """ Disconnect from the current kernel manager (if any) and set a new
             kernel manager.
         """
         # Disconnect the old kernel manager, if necessary.
         if self._kernel_manager is not None:
             self._kernel_manager.started_channels.disconnect(
                 self._started_channels)
             self._kernel_manager.stopped_channels.disconnect(
                 self._stopped_channels)
 
             # Disconnect the old kernel manager's channels.
             sub = self._kernel_manager.sub_channel
             xreq = self._kernel_manager.xreq_channel
             rep = self._kernel_manager.rep_channel
             sub.message_received.disconnect(self._handle_sub)
             xreq.execute_reply.disconnect(self._handle_execute_reply)
             xreq.complete_reply.disconnect(self._handle_complete_reply)
             xreq.object_info_reply.disconnect(self._handle_object_info_reply)
-            rep.readline_requested.disconnect(self._handle_req)
+            rep.input_requested.disconnect(self._handle_req)
 
             # Handle the case where the old kernel manager is still listening.
             if self._kernel_manager.channels_running:
                 self._stopped_channels()
 
         # Set the new kernel manager.
         self._kernel_manager = kernel_manager
         if kernel_manager is None:
             return
 
         # Connect the new kernel manager.
         kernel_manager.started_channels.connect(self._started_channels)
         kernel_manager.stopped_channels.connect(self._stopped_channels)
 
         # Connect the new kernel manager's channels.
         sub = kernel_manager.sub_channel
         xreq = kernel_manager.xreq_channel
         rep = kernel_manager.rep_channel
         sub.message_received.connect(self._handle_sub)
         xreq.execute_reply.connect(self._handle_execute_reply)
         xreq.complete_reply.connect(self._handle_complete_reply)
         xreq.object_info_reply.connect(self._handle_object_info_reply)
-        rep.readline_requested.connect(self._handle_req)
+        rep.input_requested.connect(self._handle_req)
         
         # Handle the case where the kernel manager started channels before
         # we connected.
         if kernel_manager.channels_running:
             self._started_channels()
 
     kernel_manager = property(_get_kernel_manager, _set_kernel_manager)
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' protected interface
     #---------------------------------------------------------------------------
 
     def _call_tip(self):
         """ Shows a call tip, if appropriate, at the current cursor location.
         """
         # Decide if it makes sense to show a call tip
         cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.Left)
         document = self.document()
         if document.characterAt(cursor.position()).toAscii() != '(':
             return False
         context = self._get_context(cursor)
         if not context:
             return False
 
         # Send the metadata request to the kernel
         name = '.'.join(context)
         self._calltip_id = self.kernel_manager.xreq_channel.object_info(name)
         self._calltip_pos = self.textCursor().position()
         return True
 
     def _complete(self):
         """ Performs completion at the current cursor location.
         """
         # Decide if it makes sense to do completion
         context = self._get_context()
         if not context:
             return False
 
         # Send the completion request to the kernel
         text = '.'.join(context)
         self._complete_id = self.kernel_manager.xreq_channel.complete(
             text, self.input_buffer_cursor_line, self.input_buffer)
         self._complete_pos = self.textCursor().position()
         return True
 
     def _get_banner(self):
         """ Gets a banner to display at the beginning of a session.
         """
         banner = 'Python %s on %s\nType "help", "copyright", "credits" or ' \
             '"license" for more information.'
         return banner % (sys.version, sys.platform)
 
     def _get_context(self, cursor=None):
         """ Gets the context at the current cursor location.
         """
         if cursor is None:
             cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.StartOfLine, 
                             QtGui.QTextCursor.KeepAnchor)
         text = str(cursor.selection().toPlainText())
         return self._completion_lexer.get_context(text)
 
     def _interrupt_kernel(self):
         """ Attempts to the interrupt the kernel.
         """
         if self.kernel_manager.has_kernel:
             self.kernel_manager.signal_kernel(signal.SIGINT)
         else:
             self.appendPlainText('Kernel process is either remote or '
                                  'unspecified. Cannot interrupt.\n')
 
     def _show_interpreter_prompt(self):
         """ Shows a prompt for the interpreter.
         """
         self._show_prompt('>>> ')
 
     #------ Signal handlers ----------------------------------------------------
 
     def _started_channels(self):
         """ Called when the kernel manager has started listening.
         """
         self._reset()
         self.appendPlainText(self._get_banner())
         self._show_interpreter_prompt()
 
     def _stopped_channels(self):
         """ Called when the kernel manager has stopped listening.
         """
         # FIXME: Print a message here?
         pass
 
     def _document_contents_change(self, position, removed, added):
         """ Called whenever the document's content changes. Display a calltip
             if appropriate.
         """
         # Calculate where the cursor should be *after* the change:
         position += added
 
         document = self.document()
         if position == self.textCursor().position():
             self._call_tip()
 
     def _handle_req(self, req):
         # Make sure that all output from the SUB channel has been processed
         # before entering readline mode.
         self.kernel_manager.sub_channel.flush()
 
         def callback(line):
-            self.kernel_manager.rep_channel.readline(line)
-        self._readline(callback=callback)
+            self.kernel_manager.rep_channel.input(line)
+        self._readline(req['content']['prompt'], callback=callback)
 
     def _handle_sub(self, omsg):
         if self._hidden:
             return
         handler = getattr(self, '_handle_%s' % omsg['msg_type'], None)
         if handler is not None:
             handler(omsg)
 
     def _handle_pyout(self, omsg):
         self.appendPlainText(omsg['content']['data'] + '\n')
 
     def _handle_stream(self, omsg):
         self.appendPlainText(omsg['content']['data'])
         self.moveCursor(QtGui.QTextCursor.End)
         
     def _handle_execute_reply(self, reply):
         if self._hidden:
             return
 
         # Make sure that all output from the SUB channel has been processed
         # before writing a new prompt.
         self.kernel_manager.sub_channel.flush()
 
         status = reply['content']['status']
         if status == 'error':
             self._handle_execute_error(reply)
         elif status == 'aborted':
             text = "ERROR: ABORTED\n"
             self.appendPlainText(text)
         self._hidden = True
         self._show_interpreter_prompt()
         self.executed.emit(reply)
 
     def _handle_execute_error(self, reply):
         content = reply['content']
         traceback = ''.join(content['traceback'])
         self.appendPlainText(traceback)
 
     def _handle_complete_reply(self, rep):
         cursor = self.textCursor()
         if rep['parent_header']['msg_id'] == self._complete_id and \
                 cursor.position() == self._complete_pos:
             text = '.'.join(self._get_context())
             cursor.movePosition(QtGui.QTextCursor.Left, n=len(text))
             self._complete_with_items(cursor, rep['content']['matches'])
 
     def _handle_object_info_reply(self, rep):
         cursor = self.textCursor()
         if rep['parent_header']['msg_id'] == self._calltip_id and \
                 cursor.position() == self._calltip_pos:
             doc = rep['content']['docstring']
             if doc:
                 self._call_tip_widget.show_docstring(doc)

IPython/frontend/qt/kernelmanager.py

@@ -1,171 +1,171
 """ Defines a KernelManager that provides signals and slots.
 """
 
 # System library imports.
 from PyQt4 import QtCore
 import zmq
 
 # IPython imports.
 from IPython.zmq.kernelmanager import KernelManager, SubSocketChannel, \
     XReqSocketChannel, RepSocketChannel
 from util import MetaQObjectHasTraits
 
 
 class QtSubSocketChannel(SubSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyout' or 'stdout' is received.
     output_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyerr' or 'stderr' is received.
     error_received = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         SubSocketChannel.__init__(self, *args, **kw)
 
     #---------------------------------------------------------------------------
     # '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']
         if msg_type in ('pyout', 'stdout'):
             self.output_received.emit(msg)
         elif msg_type in ('pyerr', 'stderr'):
             self.error_received.emit(msg)
 
     def flush(self):
         """ Reimplemented to ensure that signals are dispatched immediately.
         """
         super(QtSubSocketChannel, self).flush()
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtXReqSocketChannel(XReqSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # 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)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         XReqSocketChannel.__init__(self, *args, **kw)
     
     #---------------------------------------------------------------------------
     # '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)
 
 
 class QtRepSocketChannel(RepSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
-    # Emitted when a readline request is received.
-    readline_requested = QtCore.pyqtSignal(object)
+    # Emitted when an input request is received.
+    input_requested = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         RepSocketChannel.__init__(self, *args, **kw)
 
     #---------------------------------------------------------------------------
     # '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 == 'readline_request':
-            self.readline_requested.emit(msg)
+        if msg_type == 'input_request':
+            self.input_requested.emit(msg)
     
 
 class QtKernelManager(KernelManager, QtCore.QObject):
     """ 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 = QtSubSocketChannel
     xreq_channel_class = QtXReqSocketChannel
     rep_channel_class = QtRepSocketChannel
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         KernelManager.__init__(self, *args, **kw)
 
     #---------------------------------------------------------------------------
     # 'KernelManager' interface
     #---------------------------------------------------------------------------
     
     def start_channels(self):
         """ Reimplemented to emit signal.
         """
         super(QtKernelManager, self).start_channels()
         self.started_channels.emit()
 
     def stop_channels(self):
         """ Reimplemented to emit signal.
         """ 
         super(QtKernelManager, self).stop_channels()
         self.stopped_channels.emit()

IPython/zmq/kernel.py

@@ -1,547 +1,488
 #!/usr/bin/env python
 """A simple interactive kernel that talks to a frontend over 0MQ.
 
 Things to do:
 
 * Finish implementing `raw_input`.
 * 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
 #-----------------------------------------------------------------------------
 
 # Standard library imports.
 import __builtin__
 from code import CommandCompiler
 from cStringIO import StringIO
 import os
 import sys
 from threading import Thread
 import time
 import traceback
 
 # System library imports.
 import zmq
 
 # Local imports.
 from IPython.external.argparse import ArgumentParser
 from session import Session, Message, extract_header
 from completer import KernelCompleter
 
 #-----------------------------------------------------------------------------
 # Kernel and stream classes
 #-----------------------------------------------------------------------------
 
-class InStream(object):
-    """ A file like object that reads from a 0MQ XREQ socket."""
-
-    def __init__(self, session, socket):
-        self.session = session
-        self.socket = socket
-
-    def close(self):
-        self.socket = None
-
-    def flush(self):
-        if self.socket is None:
-            raise ValueError('I/O operation on closed file')
-        
-    def isatty(self):
-        return False
-
-    def next(self):
-        raise IOError('Seek not supported.')
-
-    def read(self, size=-1):
-        # FIXME: Do we want another request for this?
-        string = '\n'.join(self.readlines())
-        return self._truncate(string, size)
-
-    def readline(self, size=-1):
-        if self.socket is None:
-            raise ValueError('I/O operation on closed file')
-        else:
-            content = dict(size=size)
-            msg = self.session.msg('readline_request', content=content) 
-            reply = self._request(msg)
-            line = reply['content']['line']
-            return self._truncate(line, size)
-
-    def readlines(self, sizehint=-1):
-        # Sizehint is ignored, as is permitted.
-        if self.socket is None:
-            raise ValueError('I/O operation on closed file')
-        else:
-            lines = []
-            while True:
-                line = self.readline()
-                if line:
-                    lines.append(line)
-                else:
-                    break
-            return lines
-
-    def seek(self, offset, whence=None):
-        raise IOError('Seek not supported.')
-
-    def write(self, string):
-        raise IOError('Write not supported on a read only stream.')
-
-    def writelines(self, sequence):
-        raise IOError('Write not supported on a read only stream.')
-    
-    def _request(self, msg):
-        # Flush output before making the request. This ensures, for example,
-        # that raw_input(prompt) actually gets a prompt written.
-        sys.stderr.flush()
-        sys.stdout.flush()
-
-        self.socket.send_json(msg)
-        while True:
-            try:
-                reply = self.socket.recv_json(zmq.NOBLOCK)
-            except zmq.ZMQError, e:
-                if e.errno == zmq.EAGAIN:
-                    pass
-                else:
-                    raise
-            else:
-                break
-        return reply
-
-    def _truncate(self, string, size):
-        if size >= 0:
-            if isinstance(string, str):
-                return string[:size]
-            elif isinstance(string, unicode):
-                encoded = string.encode('utf-8')[:size]
-                return encoded.decode('utf-8', 'ignore')
-        return string
-
-
 class OutStream(object):
     """A file like object that publishes the stream to a 0MQ PUB socket."""
 
     # The time interval between automatic flushes, in seconds.
     flush_interval = 0.05
 
     def __init__(self, session, pub_socket, name):
         self.session = session
         self.pub_socket = pub_socket
         self.name = name
         self.parent_header = {}
         self._new_buffer()
 
     def set_parent(self, parent):
         self.parent_header = extract_header(parent)
 
     def close(self):
         self.pub_socket = None
 
     def flush(self):
         if self.pub_socket is None:
             raise ValueError(u'I/O operation on closed file')
         else:
             data = self._buffer.getvalue()
             if data:
                 content = {u'name':self.name, u'data':data}
                 msg = self.session.msg(u'stream', content=content,
                                        parent=self.parent_header)
                 print>>sys.__stdout__, Message(msg)
                 self.pub_socket.send_json(msg)
                 
                 self._buffer.close()
                 self._new_buffer()
 
     def isatty(self):
         return False
 
     def next(self):
         raise IOError('Read not supported on a write only stream.')
 
     def read(self, size=-1):
         raise IOError('Read not supported on a write only stream.')
 
     def readline(self, size=-1):
         raise IOError('Read not supported on a write only stream.')
 
     def write(self, string):
         if self.pub_socket is None:
             raise ValueError('I/O operation on closed file')
         else:
             self._buffer.write(string)
             current_time = time.time()
             if self._start <= 0:
                 self._start = current_time
             elif current_time - self._start > self.flush_interval:
                 self.flush()
 
     def writelines(self, sequence):
         if self.pub_socket is None:
             raise ValueError('I/O operation on closed file')
         else:
             for string in sequence:
                 self.write(string)
 
     def _new_buffer(self):
         self._buffer = StringIO()
         self._start = -1
 
 
 class DisplayHook(object):
 
     def __init__(self, session, pub_socket):
         self.session = session
         self.pub_socket = pub_socket
         self.parent_header = {}
 
     def __call__(self, obj):
         if obj is None:
             return
 
         __builtin__._ = obj
         msg = self.session.msg(u'pyout', {u'data':repr(obj)},
                                parent=self.parent_header)
         self.pub_socket.send_json(msg)
 
     def set_parent(self, parent):
         self.parent_header = extract_header(parent)
 
 
 class Kernel(object):
 
-    def __init__(self, session, reply_socket, pub_socket):
+    def __init__(self, session, reply_socket, pub_socket, req_socket):
         self.session = session
         self.reply_socket = reply_socket
         self.pub_socket = pub_socket
+        self.req_socket = req_socket
         self.user_ns = {}
         self.history = []
         self.compiler = CommandCompiler()
         self.completer = KernelCompleter(self.user_ns)
         
         # Build dict of handlers for message types
         msg_types = [ 'execute_request', 'complete_request', 
                       'object_info_request' ]
         self.handlers = {}
         for msg_type in msg_types:
             self.handlers[msg_type] = getattr(self, msg_type)
 
     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()
             print>>sys.__stdout__, "Aborting:"
             print>>sys.__stdout__, Message(msg)
             msg_type = msg['msg_type']
             reply_type = msg_type.split('_')[0] + '_reply'
             reply_msg = self.session.msg(reply_type, {'status' : 'aborted'}, msg)
             print>>sys.__stdout__, Message(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 execute_request(self, ident, parent):
         try:
             code = parent[u'content'][u'code']
         except:
             print>>sys.__stderr__, "Got bad msg: "
             print>>sys.__stderr__, Message(parent)
             return
         pyin_msg = self.session.msg(u'pyin',{u'code':code}, parent=parent)
         self.pub_socket.send_json(pyin_msg)
 
         try:
             comp_code = self.compiler(code, '<zmq-kernel>')
+
+            # 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
+
+            # Configure the display hook.
             sys.displayhook.set_parent(parent)
+
             exec comp_code in self.user_ns, self.user_ns
         except:
             result = u'error'
             etype, evalue, tb = sys.exc_info()
             tb = traceback.format_exception(etype, evalue, tb)
             exc_content = {
                 u'status' : u'error',
                 u'traceback' : tb,
                 u'ename' : unicode(etype.__name__),
                 u'evalue' : unicode(evalue)
             }
             exc_msg = self.session.msg(u'pyerr', exc_content, parent)
             self.pub_socket.send_json(exc_msg)
             reply_content = exc_content
         else:
             reply_content = {'status' : 'ok'}
             
         # Flush output before sending the reply.
         sys.stderr.flush()
         sys.stdout.flush()
 
         # Send the reply.
         reply_msg = self.session.msg(u'execute_reply', reply_content, parent)
         print>>sys.__stdout__, Message(reply_msg)
         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 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:
+            print>>sys.__stderr__, "Got bad raw_input reply: "
+            print>>sys.__stderr__, Message(parent)
+            value = ''
+        return value
+
     def complete_request(self, ident, parent):
         matches = {'matches' : self.complete(parent),
                    'status' : 'ok'}
         completion_msg = self.session.send(self.reply_socket, 'complete_reply',
                                            matches, parent, ident)
         print >> sys.__stdout__, completion_msg
 
     def complete(self, msg):
         return self.completer.complete(msg.content.line, msg.content.text)
 
     def object_info_request(self, ident, parent):
         context = parent['content']['oname'].split('.')
         object_info = self.object_info(context)
         msg = self.session.send(self.reply_socket, 'object_info_reply',
                                 object_info, parent, ident)
         print >> sys.__stdout__, msg
 
     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.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 start(self):
         while True:
             ident = self.reply_socket.recv()
-            assert self.reply_socket.rcvmore(), "Unexpected missing message part."
+            assert self.reply_socket.rcvmore(), "Missing message part."
             msg = self.reply_socket.recv_json()
             omsg = Message(msg)
             print>>sys.__stdout__
             print>>sys.__stdout__, omsg
             handler = self.handlers.get(omsg.msg_type, None)
             if handler is None:
                 print >> sys.__stderr__, "UNKNOWN MESSAGE TYPE:", omsg
             else:
                 handler(ident, omsg)
 
 #-----------------------------------------------------------------------------
 # Kernel main and launch functions
 #-----------------------------------------------------------------------------
 
 class ExitPollerUnix(Thread):
     """ A Unix-specific daemon thread that terminates the program immediately 
-    when this process' parent process no longer exists.
+    when the parent process no longer exists.
     """
 
     def __init__(self):
         super(ExitPollerUnix, self).__init__()
         self.daemon = True
     
     def run(self):
         # We cannot use os.waitpid because it works only for child processes.
         from errno import EINTR
         while True:
             try:
                 if os.getppid() == 1:
                     os._exit(1)
                 time.sleep(1.0)
             except OSError, e:
                 if e.errno == EINTR:
                     continue
                 raise
 
 class ExitPollerWindows(Thread):
     """ A Windows-specific daemon thread that terminates the program immediately
     when a Win32 handle is signaled.
     """ 
     
     def __init__(self, handle):
         super(ExitPollerWindows, self).__init__()
         self.daemon = True
         self.handle = handle
 
     def run(self):
         from _subprocess import WaitForSingleObject, WAIT_OBJECT_0, INFINITE
         result = WaitForSingleObject(self.handle, INFINITE)
         if result == WAIT_OBJECT_0:
             os._exit(1)
 
 
 def bind_port(socket, ip, port):
     """ Binds the specified ZMQ socket. If the port is less than zero, a random
     port is chosen. Returns the port that was bound.
     """
     connection = 'tcp://%s' % ip
     if port <= 0:
         port = socket.bind_to_random_port(connection)
     else:
         connection += ':%i' % port
         socket.bind(connection)
     return port
 
 
 def main():
     """ Main entry point for launching a kernel.
     """
     # Parse command line arguments.
     parser = ArgumentParser()
     parser.add_argument('--ip', type=str, default='127.0.0.1',
                         help='set the kernel\'s IP address [default: local]')
     parser.add_argument('--xrep', type=int, metavar='PORT', default=0,
                         help='set the XREP channel port [default: random]')
     parser.add_argument('--pub', type=int, metavar='PORT', default=0,
                         help='set the PUB channel port [default: random]')
     parser.add_argument('--req', type=int, metavar='PORT', default=0,
                         help='set the REQ channel port [default: random]')
     if sys.platform == 'win32':
         parser.add_argument('--parent', type=int, metavar='HANDLE', 
                             default=0, help='kill this process if the process '
                             'with HANDLE dies')
     else:
         parser.add_argument('--parent', action='store_true', 
                             help='kill this process if its parent dies')
     namespace = parser.parse_args()
 
     # Create a context, a session, and the kernel sockets.
     print >>sys.__stdout__, "Starting the kernel..."
     context = zmq.Context()
     session = Session(username=u'kernel')
 
     reply_socket = context.socket(zmq.XREP)
     xrep_port = bind_port(reply_socket, namespace.ip, namespace.xrep)
     print >>sys.__stdout__, "XREP Channel on port", xrep_port
 
     pub_socket = context.socket(zmq.PUB)
     pub_port = bind_port(pub_socket, namespace.ip, namespace.pub)
     print >>sys.__stdout__, "PUB Channel on port", pub_port
 
     req_socket = context.socket(zmq.XREQ)
     req_port = bind_port(req_socket, namespace.ip, namespace.req)
     print >>sys.__stdout__, "REQ Channel on port", req_port
 
     # Redirect input streams and set a display hook.
-    sys.stdin = InStream(session, req_socket)
     sys.stdout = OutStream(session, pub_socket, u'stdout')
     sys.stderr = OutStream(session, pub_socket, u'stderr')
     sys.displayhook = DisplayHook(session, pub_socket)
 
     # Create the kernel.
-    kernel = Kernel(session, reply_socket, pub_socket)
+    kernel = Kernel(session, reply_socket, pub_socket, req_socket)
 
     # Configure this kernel/process to die on parent termination, if necessary.
     if namespace.parent:
         if sys.platform == 'win32':
             poller = ExitPollerWindows(namespace.parent)
         else:
             poller = ExitPollerUnix()
         poller.start()
 
     # Start the kernel mainloop.
     kernel.start()
 
 
 def launch_kernel(xrep_port=0, pub_port=0, req_port=0, independent=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.
 
     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.
 
     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.
     """
     import socket
     from subprocess import Popen
 
     # Find open ports as necessary.
     ports = []
     ports_needed = int(xrep_port <= 0) + int(pub_port <= 0) + int(req_port <= 0)
     for i in xrange(ports_needed):
         sock = socket.socket()
         sock.bind(('', 0))
         ports.append(sock)
     for i, sock in enumerate(ports):
         port = sock.getsockname()[1]
         sock.close()
         ports[i] = port
     if xrep_port <= 0:
         xrep_port = ports.pop(0)
     if pub_port <= 0:
         pub_port = ports.pop(0)
     if req_port <= 0:
         req_port = ports.pop(0)
         
     # Spawn a kernel.
     command = 'from IPython.zmq.kernel import main; main()'
     arguments = [ sys.executable, '-c', command, '--xrep', str(xrep_port), 
                   '--pub', str(pub_port), '--req', str(req_port) ]
     if independent:
         if sys.platform == 'win32':
             proc = Popen(['start', '/b'] + arguments, shell=True)
         else:
             proc = Popen(arguments, preexec_fn=lambda: os.setsid())
     else:
         if sys.platform == 'win32':
             from _subprocess import DuplicateHandle, GetCurrentProcess, \
                 DUPLICATE_SAME_ACCESS
             pid = GetCurrentProcess()
             handle = DuplicateHandle(pid, pid, pid, 0, 
                                      True, # Inheritable by new  processes.
                                      DUPLICATE_SAME_ACCESS)
             proc = Popen(arguments + ['--parent', str(int(handle))])
         else:
             proc = Popen(arguments + ['--parent'])
 
     return proc, xrep_port, pub_port, req_port
     
 
 if __name__ == '__main__':
     main()

IPython/zmq/kernelmanager.py

@@ -1,594 +1,587
 """Classes to manage the interaction with a running kernel.
 
 Todo
 ====
 
 * Create logger to handle debugging and console messages.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2010  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports.
 from Queue import Queue, Empty
 from subprocess import Popen
 from threading import Thread
 import time
 
 # System library imports.
 import zmq
 from zmq import POLLIN, POLLOUT, POLLERR
 from zmq.eventloop import ioloop
 
 # Local imports.
 from IPython.utils.traitlets import HasTraits, Any, Instance, Type
 from kernel import launch_kernel
 from session import Session
 
 #-----------------------------------------------------------------------------
 # Constants and exceptions
 #-----------------------------------------------------------------------------
 
 LOCALHOST = '127.0.0.1'
 
 class InvalidPortNumber(Exception):
     pass
 
 #-----------------------------------------------------------------------------
 # ZMQ Socket Channel classes
 #-----------------------------------------------------------------------------
 
 class ZmqSocketChannel(Thread):
     """The base class for the channels that use ZMQ sockets.
     """
     context = None
     session = None
     socket = None
     ioloop = None
     iostate = None
     _address = None
 
     def __init__(self, context, session, address):
         """Create a channel
 
         Parameters
         ----------
         context : zmq.Context
             The ZMQ context to use.
         session : session.Session
             The session to use.
         address : tuple
             Standard (ip, port) tuple that the kernel is listening on.
         """
         super(ZmqSocketChannel, self).__init__()
         self.daemon = True
 
         self.context = context
         self.session = session
         if address[1] == 0:
             message = 'The port number for a channel cannot be 0.'
             raise InvalidPortNumber(message)
         self._address = address
 
     def stop(self):
         """Stop the channel's activity.
 
         This calls :method:`Thread.join` and returns when the thread
         terminates. :class:`RuntimeError` will be raised if 
         :method:`self.start` is called again.
         """
         self.join()
 
     @property
     def address(self):
         """Get the channel's address as an (ip, port) tuple.
         
         By the default, the address is (localhost, 0), where 0 means a random
         port.
         """
         return self._address
 
     def add_io_state(self, state):
         """Add IO state to the eventloop.
 
         Parameters
         ----------
         state : zmq.POLLIN|zmq.POLLOUT|zmq.POLLERR
             The IO state flag to set.
 
         This is thread safe as it uses the thread safe IOLoop.add_callback.
         """
         def add_io_state_callback():
             if not self.iostate & state:
                 self.iostate = self.iostate | state
                 self.ioloop.update_handler(self.socket, self.iostate)
         self.ioloop.add_callback(add_io_state_callback)
 
     def drop_io_state(self, state):
         """Drop IO state from the eventloop.
 
         Parameters
         ----------
         state : zmq.POLLIN|zmq.POLLOUT|zmq.POLLERR
             The IO state flag to set.
 
         This is thread safe as it uses the thread safe IOLoop.add_callback.
         """
         def drop_io_state_callback():
             if self.iostate & state:
                 self.iostate = self.iostate & (~state)
                 self.ioloop.update_handler(self.socket, self.iostate)
         self.ioloop.add_callback(drop_io_state_callback)
 
 
 class XReqSocketChannel(ZmqSocketChannel):
     """The XREQ channel for issues request/replies to the kernel.
     """
 
     command_queue = None
 
     def __init__(self, context, session, address):
         self.command_queue = Queue()
         super(XReqSocketChannel, self).__init__(context, session, address)
 
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.XREQ)
         self.socket.setsockopt(zmq.IDENTITY, self.session.session)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.ioloop = ioloop.IOLoop()
         self.iostate = POLLERR|POLLIN
         self.ioloop.add_handler(self.socket, self._handle_events, 
                                 self.iostate)
         self.ioloop.start()
 
     def stop(self):
         self.ioloop.stop()
         super(XReqSocketChannel, self).stop()
 
     def call_handlers(self, msg):
         """This method is called in the ioloop thread when a message arrives.
 
         Subclasses should override this method to handle incoming messages.
         It is important to remember that this method is called in the thread
         so that some logic must be done to ensure that the application leve
         handlers are called in the application thread.
         """
         raise NotImplementedError('call_handlers must be defined in a subclass.')
 
     def execute(self, code):
         """Execute code in the kernel.
 
         Parameters
         ----------
         code : str
             A string of Python code.
 
         Returns
         -------
         The msg_id of the message sent.
         """
         # Create class for content/msg creation. Related to, but possibly
         # not in Session.
         content = dict(code=code)
         msg = self.session.msg('execute_request', content)
         self._queue_request(msg)
         return msg['header']['msg_id']
 
     def complete(self, text, line, block=None):
         """Tab complete text, line, block in the kernel's namespace.
 
         Parameters
         ----------
         text : str
             The text to complete.
         line : str
             The full line of text that is the surrounding context for the 
             text to complete.
         block : str
             The full block of code in which the completion is being requested.
 
         Returns
         -------
         The msg_id of the message sent.
         """
         content = dict(text=text, line=line)
         msg = self.session.msg('complete_request', content)
         self._queue_request(msg)
         return msg['header']['msg_id']
 
     def object_info(self, oname):
         """Get metadata information about an object.
 
         Parameters
         ----------
         oname : str
             A string specifying the object name.
         
         Returns
         -------
         The msg_id of the message sent.
         """
         content = dict(oname=oname)
         msg = self.session.msg('object_info_request', content)
         self._queue_request(msg)
         return msg['header']['msg_id']
 
     def _handle_events(self, socket, events):
         if events & POLLERR:
             self._handle_err()
         if events & POLLOUT:
             self._handle_send()
         if events & POLLIN:
             self._handle_recv()
 
     def _handle_recv(self):
         msg = self.socket.recv_json()
         self.call_handlers(msg)
 
     def _handle_send(self):
         try:
             msg = self.command_queue.get(False)
         except Empty:
             pass
         else:
             self.socket.send_json(msg)
         if self.command_queue.empty():
             self.drop_io_state(POLLOUT)
 
     def _handle_err(self):
         # We don't want to let this go silently, so eventually we should log.
         raise zmq.ZMQError()
 
     def _queue_request(self, msg):
         self.command_queue.put(msg)
         self.add_io_state(POLLOUT)
 
 
 class SubSocketChannel(ZmqSocketChannel):
     """The SUB channel which listens for messages that the kernel publishes.
     """
 
     def __init__(self, context, session, address):
         super(SubSocketChannel, self).__init__(context, session, address)
 
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.SUB)
         self.socket.setsockopt(zmq.SUBSCRIBE,'')
         self.socket.setsockopt(zmq.IDENTITY, self.session.session)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.ioloop = ioloop.IOLoop()
         self.iostate = POLLIN|POLLERR
         self.ioloop.add_handler(self.socket, self._handle_events, 
                                 self.iostate)
         self.ioloop.start()
 
     def stop(self):
         self.ioloop.stop()
         super(SubSocketChannel, self).stop()
 
     def call_handlers(self, msg):
         """This method is called in the ioloop thread when a message arrives.
 
         Subclasses should override this method to handle incoming messages.
         It is important to remember that this method is called in the thread
         so that some logic must be done to ensure that the application leve
         handlers are called in the application thread.
         """
         raise NotImplementedError('call_handlers must be defined in a subclass.')
 
     def flush(self, timeout=1.0):
         """Immediately processes all pending messages on the SUB channel.
 
         This method is thread safe.
 
         Parameters
         ----------
         timeout : float, optional
             The maximum amount of time to spend flushing, in seconds. The
             default is one second.
         """
         # We do the IOLoop callback process twice to ensure that the IOLoop
         # gets to perform at least one full poll.
         stop_time = time.time() + timeout
         for i in xrange(2):
             self._flushed = False
             self.ioloop.add_callback(self._flush)
             while not self._flushed and time.time() < stop_time:
                 time.sleep(0.01)
 
     def _handle_events(self, socket, events):
         # Turn on and off POLLOUT depending on if we have made a request
         if events & POLLERR:
             self._handle_err()
         if events & POLLIN:
             self._handle_recv()
 
     def _handle_err(self):
         # We don't want to let this go silently, so eventually we should log.
         raise zmq.ZMQError()
 
     def _handle_recv(self):
         # Get all of the messages we can
         while True:
             try:
                 msg = self.socket.recv_json(zmq.NOBLOCK)
             except zmq.ZMQError:
                 # Check the errno?
                 # Will this tigger POLLERR?
                 break
             else:
                 self.call_handlers(msg)
 
     def _flush(self):
         """Callback for :method:`self.flush`."""
         self._flushed = True
 
 
 class RepSocketChannel(ZmqSocketChannel):
     """A reply channel to handle raw_input requests that the kernel makes."""
 
     msg_queue = None
 
     def __init__(self, context, session, address):
         self.msg_queue = Queue()
         super(RepSocketChannel, self).__init__(context, session, address)
 
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.XREQ)
         self.socket.setsockopt(zmq.IDENTITY, self.session.session)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.ioloop = ioloop.IOLoop()
         self.iostate = POLLERR|POLLIN
         self.ioloop.add_handler(self.socket, self._handle_events, 
                                 self.iostate)
         self.ioloop.start()
 
     def stop(self):
         self.ioloop.stop()
         super(RepSocketChannel, self).stop()
 
     def call_handlers(self, msg):
         """This method is called in the ioloop thread when a message arrives.
 
         Subclasses should override this method to handle incoming messages.
         It is important to remember that this method is called in the thread
         so that some logic must be done to ensure that the application leve
         handlers are called in the application thread.
         """
         raise NotImplementedError('call_handlers must be defined in a subclass.')
 
-    def readline(self, line):
-        """A send a line of raw input to the kernel.
-
-        Parameters
-        ----------
-        line : str
-            The line of the input.
-        """
-        content = dict(line=line)
-        msg = self.session.msg('readline_reply', content)
+    def input(self, string):
+        """Send a string of raw input to the kernel."""
+        content = dict(value=string)
+        msg = self.session.msg('input_reply', content)
         self._queue_reply(msg)
 
     def _handle_events(self, socket, events):
         if events & POLLERR:
             self._handle_err()
         if events & POLLOUT:
             self._handle_send()
         if events & POLLIN:
             self._handle_recv()
 
     def _handle_recv(self):
         msg = self.socket.recv_json()
         self.call_handlers(msg)
 
     def _handle_send(self):
         try:
             msg = self.msg_queue.get(False)
         except Empty:
             pass
         else:
             self.socket.send_json(msg)
         if self.msg_queue.empty():
             self.drop_io_state(POLLOUT)
 
     def _handle_err(self):
         # We don't want to let this go silently, so eventually we should log.
         raise zmq.ZMQError()
 
     def _queue_reply(self, msg):
         self.msg_queue.put(msg)
         self.add_io_state(POLLOUT)
 
 
 #-----------------------------------------------------------------------------
 # Main kernel manager class
 #-----------------------------------------------------------------------------
 
 class KernelManager(HasTraits):
     """ Manages a kernel for a frontend.
 
     The SUB channel is for the frontend to receive messages published by the
     kernel.
         
     The REQ channel is for the frontend to make requests of the kernel.
     
     The REP channel is for the kernel to request stdin (raw_input) from the
     frontend.
     """
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context)
 
     # The Session to use for communication with the kernel.
     session = Instance(Session)
 
+    # The kernel process with which the KernelManager is communicating.
+    kernel = Instance(Popen)
+
     # The classes to use for the various channels.
     xreq_channel_class = Type(XReqSocketChannel)
     sub_channel_class = Type(SubSocketChannel)
     rep_channel_class = Type(RepSocketChannel)
     
     # Protected traits.
-    _kernel = Instance(Popen)
     _xreq_address = Any
     _sub_address = Any
     _rep_address = Any
     _xreq_channel = Any
     _sub_channel = Any
     _rep_channel = Any
 
     def __init__(self, xreq_address=None, sub_address=None, rep_address=None,
                  context=None, session=None):
         super(KernelManager, self).__init__()
         self._xreq_address = (LOCALHOST, 0) if xreq_address is None else xreq_address
         self._sub_address = (LOCALHOST, 0) if sub_address is None else sub_address
         self._rep_address = (LOCALHOST, 0) if rep_address is None else rep_address
         self.context = zmq.Context() if context is None else context
         self.session = Session() if session is None else session
 
     #--------------------------------------------------------------------------
     # Channel management methods:
     #--------------------------------------------------------------------------
 
     def start_channels(self):
         """Starts the channels for this kernel.
 
         This will create the channels if they do not exist and then start
         them. If port numbers of 0 are being used (random ports) then you
         must first call :method:`start_kernel`. If the channels have been
         stopped and you call this, :class:`RuntimeError` will be raised.
         """
         self.xreq_channel.start()
         self.sub_channel.start()
         self.rep_channel.start()
 
     def stop_channels(self):
         """Stops the channels for this kernel.
 
         This stops the channels by joining their threads. If the channels
         were not started, :class:`RuntimeError` will be raised.
         """
         self.xreq_channel.stop()
         self.sub_channel.stop()
         self.rep_channel.stop()
 
     @property
     def channels_running(self):
         """Are all of the channels created and running?"""
         return self.xreq_channel.is_alive() \
             and self.sub_channel.is_alive() \
             and self.rep_channel.is_alive()
 
     #--------------------------------------------------------------------------
     # Kernel process management methods:
     #--------------------------------------------------------------------------
 
     def start_kernel(self):
         """Starts a kernel process and configures the manager to use it.
 
         If random ports (port=0) are being used, this method must be called
         before the channels are created.
         """
         xreq, sub, rep = self.xreq_address, self.sub_address, self.rep_address
         if xreq[0] != LOCALHOST or sub[0] != LOCALHOST or rep[0] != LOCALHOST:
             raise RuntimeError("Can only launch a kernel on localhost."
                                "Make sure that the '*_address' attributes are "
                                "configured properly.")
 
-        kernel, xrep, pub, req = launch_kernel(
+        self.kernel, xrep, pub, req = launch_kernel(
             xrep_port=xreq[1], pub_port=sub[1], req_port=rep[1])
-        self._kernel = kernel
         self._xreq_address = (LOCALHOST, xrep)
         self._sub_address = (LOCALHOST, pub)
         self._rep_address = (LOCALHOST, req)
 
     @property
     def has_kernel(self):
         """Returns whether a kernel process has been specified for the kernel
         manager.
-
-        A kernel process can be set via 'start_kernel' or 'set_kernel'.
         """
-        return self._kernel is not None
+        return self.kernel is not None
 
     def kill_kernel(self):
         """ Kill the running kernel. """
-        if self._kernel is not None:
-            self._kernel.kill()
-            self._kernel = None
+        if self.kernel is not None:
+            self.kernel.kill()
+            self.kernel = None
         else:
             raise RuntimeError("Cannot kill kernel. No kernel is running!")
 
     def signal_kernel(self, signum):
         """ Sends a signal to the kernel. """
-        if self._kernel is not None:
-            self._kernel.send_signal(signum)
+        if self.kernel is not None:
+            self.kernel.send_signal(signum)
         else:
             raise RuntimeError("Cannot signal kernel. No kernel is running!")
 
     @property
     def is_alive(self):
         """Is the kernel process still running?"""
-        if self._kernel is not None:
-            if self._kernel.poll() is None:
+        if self.kernel is not None:
+            if self.kernel.poll() is None:
                 return True
             else:
                 return False
         else:
             # We didn't start the kernel with this KernelManager so we don't
             # know if it is running. We should use a heartbeat for this case.
             return True
 
     #--------------------------------------------------------------------------
     # Channels used for communication with the kernel:
     #--------------------------------------------------------------------------
 
     @property
     def xreq_channel(self):
         """Get the REQ socket channel object to make requests of the kernel."""
         if self._xreq_channel is None:
             self._xreq_channel = self.xreq_channel_class(self.context, 
                                                          self.session,
                                                          self.xreq_address)
         return self._xreq_channel
 
     @property
     def sub_channel(self):
         """Get the SUB socket channel object."""
         if self._sub_channel is None:
             self._sub_channel = self.sub_channel_class(self.context,
                                                        self.session,
                                                        self.sub_address)
         return self._sub_channel
 
     @property
     def rep_channel(self):
         """Get the REP socket channel object to handle stdin (raw_input)."""
         if self._rep_channel is None:
             self._rep_channel = self.rep_channel_class(self.context, 
                                                        self.session,
                                                        self.rep_address)
         return self._rep_channel
 
     @property
     def xreq_address(self):
         return self._xreq_address
 
     @property
     def sub_address(self):
         return self._sub_address
 
     @property
     def rep_address(self):
         return self._rep_address