First cut at allowing the kernel to be restarted from the frontend.

IPython/frontend/qt/console/console_widget.py

@@ -430,12 +430,6 b' class ConsoleWidget(QtGui.QWidget):'
         """
         raise NotImplementedError
 
-    def _execute_interrupt(self):
-        """ Attempts to stop execution. Returns whether this method has an
-            implementation.
-        """
-        return False
-
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
@@ -575,10 +569,7 b' class ConsoleWidget(QtGui.QWidget):'
             intercepted = True
 
         elif ctrl_down:
-            if key == QtCore.Qt.Key_C:
-                intercepted = self._executing and self._execute_interrupt()
-
-            elif key == QtCore.Qt.Key_K:
+            if key == QtCore.Qt.Key_K:
                 if self._in_buffer(position):
                     cursor.movePosition(QtGui.QTextCursor.EndOfLine,
                                         QtGui.QTextCursor.KeepAnchor)

IPython/frontend/qt/console/frontend_widget.py

@@ -72,12 +72,22 b' class FrontendHighlighter(PygmentsHighlighter):'
 class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):
     """ A Qt frontend for a generic Python kernel.
     """
+
+    # An option and corresponding signal for overriding the default kernel
+    # interrupt behavior.
+    custom_interrupt = False
+    custom_interrupt_requested = QtCore.pyqtSignal()
+
+    # An option and corresponding signal for overriding the default kernel
+    # restart behavior.
+    custom_restart = False
+    custom_restart_requested = QtCore.pyqtSignal()
    
     # Emitted when an 'execute_reply' has been received from the kernel and
     # processed by the FrontendWidget.
     executed = QtCore.pyqtSignal(object)
-
-    # Protected class attributes.
+    
+    # Protected class variables.
     _highlighter_class = FrontendHighlighter
     _input_splitter_class = InputSplitter
 
@@ -123,13 +133,6 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
         """
         self.kernel_manager.xreq_channel.execute(source, hidden)
         self._hidden = hidden
-
-    def _execute_interrupt(self):
-        """ Attempts to stop execution. Returns whether this method has an
-            implementation.
-        """
-        self._interrupt_kernel()
-        return True
         
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
@@ -163,6 +166,19 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
     # 'ConsoleWidget' protected interface
     #---------------------------------------------------------------------------
 
+    def _event_filter_console_keypress(self, event):
+        """ Reimplemented to allow execution interruption.
+        """
+        key = event.key()
+        if self._executing and self._control_key_down(event.modifiers()):
+            if key == QtCore.Qt.Key_C:
+                self._kernel_interrupt()
+                return True
+            elif key == QtCore.Qt.Key_Period:
+                self._kernel_restart()
+                return True
+        return super(FrontendWidget, self)._event_filter_console_keypress(event)
+
     def _show_continuation_prompt(self):
         """ Reimplemented for auto-indentation.
         """
@@ -324,15 +340,36 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
         text = str(cursor.selection().toPlainText())
         return self._completion_lexer.get_context(text)
 
-    def _interrupt_kernel(self):
-        """ Attempts to the interrupt the kernel.
+    def _kernel_interrupt(self):
+        """ Attempts to interrupt the running kernel.
         """
-        if self.kernel_manager.has_kernel:
+        if self.custom_interrupt:
+            self.custom_interrupt_requested.emit()
+        elif self.kernel_manager.has_kernel:
             self.kernel_manager.signal_kernel(signal.SIGINT)
         else:
             self._append_plain_text('Kernel process is either remote or '
                                     'unspecified. Cannot interrupt.\n')
 
+    def _kernel_restart(self):
+        """ Attempts to restart the running kernel.
+        """
+        if self.custom_restart:
+            self.custom_restart_requested.emit()
+        elif self.kernel_manager.has_kernel:
+            try:
+                self.kernel_manager.restart_kernel()
+            except RuntimeError:
+                message = 'Kernel started externally. Cannot restart.\n'
+                self._append_plain_text(message)
+            else:
+                self._stopped_channels()
+                self._append_plain_text('Kernel restarting...\n')
+                self._show_interpreter_prompt()
+        else:
+            self._append_plain_text('Kernel process is either remote or '
+                                    'unspecified. Cannot restart.\n')
+
     def _process_execute_abort(self, msg):
         """ Process a reply for an aborted execution request.
         """

IPython/frontend/qt/console/rich_ipython_widget.py

@@ -1,5 +1,3 b''
-import os
-
 # System library imports
 from PyQt4 import QtCore, QtGui
 

IPython/zmq/kernelmanager.py

@@ -482,6 +482,7 b' class KernelManager(HasTraits):'
     rep_channel_class = Type(RepSocketChannel)
     
     # Protected traits.
+    _launch_args = Any
     _xreq_channel = Any
     _sub_channel = Any
     _rep_channel = Any
@@ -523,7 +524,7 b' class KernelManager(HasTraits):'
     # Kernel process management methods:
     #--------------------------------------------------------------------------
 
-    def start_kernel(self, ipython=True, **kw):
+    def start_kernel(self, **kw):
         """Starts a kernel process and configures the manager to use it.
 
         If random ports (port=0) are being used, this method must be called
@@ -540,7 +541,8 b' class KernelManager(HasTraits):'
                                "Make sure that the '*_address' attributes are "
                                "configured properly.")
 
-        if ipython:
+        self._launch_args = kw.copy()
+        if kw.pop('ipython', True):
             from ipkernel import launch_kernel as launch
         else:
             from pykernel import launch_kernel as launch
@@ -550,6 +552,19 b' class KernelManager(HasTraits):'
         self.sub_address = (LOCALHOST, pub)
         self.rep_address = (LOCALHOST, req)
 
+    def restart_kernel(self):
+        """Restarts a kernel with the same arguments that were used to launch
+        it. If the old kernel was launched with random ports, the same ports
+        will be used for the new kernel.
+        """
+        if self._launch_args is None:
+            raise RuntimeError("Cannot restart the kernel. "
+                               "No previous call to 'start_kernel'.")
+        else:
+            if self.has_kernel:
+                self.kill_kernel()
+            self.start_kernel(*self._launch_args)
+
     @property
     def has_kernel(self):
         """Returns whether a kernel process has been specified for the kernel