Remove unused copies of validate_string_dict

IPython/kernel/blocking/channels.py

@@ -1,107 +1,92
 """Blocking channels
 
 Useful for test suites and blocking terminal interfaces.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 try:
     from queue import Queue, Empty  # Py 3
 except ImportError:
     from Queue import Queue, Empty  # Py 2
 
-from IPython.utils.py3compat import string_types, iteritems
-
-# some utilities to validate message structure, these might get moved elsewhere
-# if they prove to have more generic utility
-
-def validate_string_dict(dct):
-    """Validate that the input is a dict with string keys and values.
-
-    Raises ValueError if not."""
-    for k,v in iteritems(dct):
-        if not isinstance(k, string_types):
-            raise ValueError('key %r in dict must be a string' % k)
-        if not isinstance(v, string_types):
-            raise ValueError('value %r in dict must be a string' % v)
-
 
 class ZMQSocketChannel(object):
     """A ZMQ socket in a simple blocking API"""
     session = None
     socket = None
     stream = None
     _exiting = False
     proxy_methods = []
 
     def __init__(self, socket, session, loop=None):
         """Create a channel.
 
         Parameters
         ----------
         socket : :class:`zmq.Socket`
             The ZMQ socket to use.
         session : :class:`session.Session`
             The session to use.
         loop
             Unused here, for other implementations
         """
         super(ZMQSocketChannel, self).__init__()
 
         self.socket = socket
         self.session = session
 
     def _recv(self, **kwargs):
         msg = self.socket.recv_multipart(**kwargs)
         ident,smsg = self.session.feed_identities(msg)
         return self.session.deserialize(smsg)
 
     def get_msg(self, block=True, timeout=None):
         """ Gets a message if there is one that is ready. """
         if block:
             if timeout is not None:
                 timeout *= 1000  # seconds to ms
             ready = self.socket.poll(timeout)
         else:
             ready = self.socket.poll(timeout=0)
 
         if ready:
             return self._recv()
         else:
             raise Empty
 
     def get_msgs(self):
         """ Get all messages that are currently ready. """
         msgs = []
         while True:
             try:
                 msgs.append(self.get_msg(block=False))
             except Empty:
                 break
         return msgs
 
     def msg_ready(self):
         """ Is there a message that has been received? """
         return bool(self.socket.poll(timeout=0))
 
     def close(self):
         if self.socket is not None:
             try:
                 self.socket.close(linger=0)
             except Exception:
                 pass
             self.socket = None
     stop =  close
 
     def is_alive(self):
         return (self.socket is not None)
 
     def _queue_send(self, msg):
         """Pass a message to the ZMQ socket to send
         """
         self.session.send(self.socket, msg)
 
     def start(self):
         pass
 

IPython/kernel/channels.py

@@ -1,245 +1,226
 """Base classes to manage a Client's interaction with a running kernel"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from __future__ import absolute_import
 
 import atexit
 import errno
 from threading import Thread
 import time
 
 import zmq
 # import ZMQError in top-level namespace, to avoid ugly attribute-error messages
 # during garbage collection of threads at exit:
 from zmq import ZMQError
-from zmq.eventloop import ioloop, zmqstream
 
 from IPython.core.release import kernel_protocol_version_info
 
 from .channelsabc import HBChannelABC
-from IPython.utils.py3compat import string_types, iteritems
 
 #-----------------------------------------------------------------------------
 # Constants and exceptions
 #-----------------------------------------------------------------------------
 
 major_protocol_version = kernel_protocol_version_info[0]
 
 class InvalidPortNumber(Exception):
     pass
 
-#-----------------------------------------------------------------------------
-# Utility functions
-#-----------------------------------------------------------------------------
-
-# some utilities to validate message structure, these might get moved elsewhere
-# if they prove to have more generic utility
-
-def validate_string_dict(dct):
-    """Validate that the input is a dict with string keys and values.
-
-    Raises ValueError if not."""
-    for k,v in iteritems(dct):
-        if not isinstance(k, string_types):
-            raise ValueError('key %r in dict must be a string' % k)
-        if not isinstance(v, string_types):
-            raise ValueError('value %r in dict must be a string' % v)
-
 
 def make_shell_socket(context, identity, address):
     socket = context.socket(zmq.DEALER)
     socket.linger = 1000
     socket.setsockopt(zmq.IDENTITY, identity)
     socket.connect(address)
     return socket
 
 def make_iopub_socket(context, identity, address):
     socket = context.socket(zmq.SUB)
     socket.linger = 1000
     socket.setsockopt(zmq.SUBSCRIBE,b'')
     socket.setsockopt(zmq.IDENTITY, identity)
     socket.connect(address)
     return socket
 
 def make_stdin_socket(context, identity, address):
     socket = context.socket(zmq.DEALER)
     socket.linger = 1000
     socket.setsockopt(zmq.IDENTITY, identity)
     socket.connect(address)
     return socket
 
 class HBChannel(Thread):
     """The heartbeat channel which monitors the kernel heartbeat.
 
     Note that the heartbeat channel is paused by default. As long as you start
     this channel, the kernel manager will ensure that it is paused and un-paused
     as appropriate.
     """
     context = None
     session = None
     socket = None
     address = None
     _exiting = False
 
     time_to_dead = 1.
     poller = None
     _running = None
     _pause = None
     _beating = None
 
     def __init__(self, context, session, address):
         """Create the heartbeat monitor thread.
 
         Parameters
         ----------
         context : :class:`zmq.Context`
             The ZMQ context to use.
         session : :class:`session.Session`
             The session to use.
         address : zmq url
             Standard (ip, port) tuple that the kernel is listening on.
         """
         super(HBChannel, self).__init__()
         self.daemon = True
 
         self.context = context
         self.session = session
         if isinstance(address, tuple):
             if address[1] == 0:
                 message = 'The port number for a channel cannot be 0.'
                 raise InvalidPortNumber(message)
             address = "tcp://%s:%i" % address
         self.address = address
         atexit.register(self._notice_exit)
 
         self._running = False
         self._pause = True
         self.poller = zmq.Poller()
 
     def _notice_exit(self):
         self._exiting = True
 
     def _create_socket(self):
         if self.socket is not None:
             # close previous socket, before opening a new one
             self.poller.unregister(self.socket)
             self.socket.close()
         self.socket = self.context.socket(zmq.REQ)
         self.socket.linger = 1000
         self.socket.connect(self.address)
 
         self.poller.register(self.socket, zmq.POLLIN)
 
     def _poll(self, start_time):
         """poll for heartbeat replies until we reach self.time_to_dead.
 
         Ignores interrupts, and returns the result of poll(), which
         will be an empty list if no messages arrived before the timeout,
         or the event tuple if there is a message to receive.
         """
 
         until_dead = self.time_to_dead - (time.time() - start_time)
         # ensure poll at least once
         until_dead = max(until_dead, 1e-3)
         events = []
         while True:
             try:
                 events = self.poller.poll(1000 * until_dead)
             except ZMQError as e:
                 if e.errno == errno.EINTR:
                     # ignore interrupts during heartbeat
                     # this may never actually happen
                     until_dead = self.time_to_dead - (time.time() - start_time)
                     until_dead = max(until_dead, 1e-3)
                     pass
                 else:
                     raise
             except Exception:
                 if self._exiting:
                     break
                 else:
                     raise
             else:
                 break
         return events
 
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self._create_socket()
         self._running = True
         self._beating = True
 
         while self._running:
             if self._pause:
                 # just sleep, and skip the rest of the loop
                 time.sleep(self.time_to_dead)
                 continue
 
             since_last_heartbeat = 0.0
             # io.rprint('Ping from HB channel') # dbg
             # no need to catch EFSM here, because the previous event was
             # either a recv or connect, which cannot be followed by EFSM
             self.socket.send(b'ping')
             request_time = time.time()
             ready = self._poll(request_time)
             if ready:
                 self._beating = True
                 # the poll above guarantees we have something to recv
                 self.socket.recv()
                 # sleep the remainder of the cycle
                 remainder = self.time_to_dead - (time.time() - request_time)
                 if remainder > 0:
                     time.sleep(remainder)
                 continue
             else:
                 # nothing was received within the time limit, signal heart failure
                 self._beating = False
                 since_last_heartbeat = time.time() - request_time
                 self.call_handlers(since_last_heartbeat)
                 # and close/reopen the socket, because the REQ/REP cycle has been broken
                 self._create_socket()
                 continue
 
     def pause(self):
         """Pause the heartbeat."""
         self._pause = True
 
     def unpause(self):
         """Unpause the heartbeat."""
         self._pause = False
 
     def is_beating(self):
         """Is the heartbeat running and responsive (and not paused)."""
         if self.is_alive() and not self._pause and self._beating:
             return True
         else:
             return False
 
     def stop(self):
         """Stop the channel's event loop and join its thread."""
         self._running = False
         self.join()
         self.close()
 
     def close(self):
         if self.socket is not None:
             try:
                 self.socket.close(linger=0)
             except Exception:
                 pass
             self.socket = None
 
     def call_handlers(self, since_last_heartbeat):
         """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 level
         handlers are called in the application thread.
         """
         pass
 
 
 HBChannelABC.register(HBChannel)

IPython/kernel/client.py

@@ -1,375 +1,389
 """Base class to manage the interaction with a running kernel"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from __future__ import absolute_import
-from IPython.kernel.channels import validate_string_dict, major_protocol_version
-from IPython.utils.py3compat import string_types
+from IPython.kernel.channels import major_protocol_version
+from IPython.utils.py3compat import string_types, iteritems
 
 import zmq
 
 from IPython.utils.traitlets import (
     Any, Instance, Type,
 )
 
 from .channelsabc import (ChannelABC, HBChannelABC)
 from .channels import (
     make_shell_socket, make_stdin_socket, make_iopub_socket
 )
 from .clientabc import KernelClientABC
 from .connect import ConnectionFileMixin
 
 
+# some utilities to validate message structure, these might get moved elsewhere
+# if they prove to have more generic utility
+
+def validate_string_dict(dct):
+    """Validate that the input is a dict with string keys and values.
+
+    Raises ValueError if not."""
+    for k,v in iteritems(dct):
+        if not isinstance(k, string_types):
+            raise ValueError('key %r in dict must be a string' % k)
+        if not isinstance(v, string_types):
+            raise ValueError('value %r in dict must be a string' % v)
+
+
 class KernelClient(ConnectionFileMixin):
     """Communicates with a single kernel on any host via zmq channels.
 
     There are four channels associated with each kernel:
 
     * shell: for request/reply calls to the kernel.
     * iopub: for the kernel to publish results to frontends.
     * hb: for monitoring the kernel's heartbeat.
     * stdin: for frontends to reply to raw_input calls in the kernel.
 
     The methods of the channels are exposed as methods of the client itself
     (KernelClient.execute, complete, history, etc.).
     See the channels themselves for documentation of these methods.
 
     """
 
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context)
     def _context_default(self):
         return zmq.Context.instance()
 
     # The classes to use for the various channels
     shell_channel_class = Type(ChannelABC)
     iopub_channel_class = Type(ChannelABC)
     stdin_channel_class = Type(ChannelABC)
     hb_channel_class = Type(HBChannelABC)
 
     # Protected traits
     _shell_channel = Any
     _iopub_channel = Any
     _stdin_channel = Any
     _hb_channel = Any
 
     # flag for whether execute requests should be allowed to call raw_input:
     allow_stdin = True
 
     #--------------------------------------------------------------------------
     # Channel proxy methods
     #--------------------------------------------------------------------------
 
     def _get_msg(channel, *args, **kwargs):
         return channel.get_msg(*args, **kwargs)
 
     def get_shell_msg(self, *args, **kwargs):
         """Get a message from the shell channel"""
         return self.shell_channel.get_msg(*args, **kwargs)
 
     def get_iopub_msg(self, *args, **kwargs):
         """Get a message from the iopub channel"""
         return self.iopub_channel.get_msg(*args, **kwargs)
 
     def get_stdin_msg(self, *args, **kwargs):
         """Get a message from the stdin channel"""
         return self.stdin_channel.get_msg(*args, **kwargs)
 
     #--------------------------------------------------------------------------
     # Channel management methods
     #--------------------------------------------------------------------------
 
     def start_channels(self, shell=True, iopub=True, stdin=True, hb=True):
         """Starts the channels for this kernel.
 
         This will create the channels if they do not exist and then start
         them (their activity runs in a thread). If port numbers of 0 are
         being used (random ports) then you must first call
         :meth:`start_kernel`. If the channels have been stopped and you
         call this, :class:`RuntimeError` will be raised.
         """
         if shell:
             self.shell_channel.start()
             self.kernel_info()
         if iopub:
             self.iopub_channel.start()
         if stdin:
             self.stdin_channel.start()
             self.allow_stdin = True
         else:
             self.allow_stdin = False
         if hb:
             self.hb_channel.start()
 
     def stop_channels(self):
         """Stops all the running channels for this kernel.
 
         This stops their event loops and joins their threads.
         """
         if self.shell_channel.is_alive():
             self.shell_channel.stop()
         if self.iopub_channel.is_alive():
             self.iopub_channel.stop()
         if self.stdin_channel.is_alive():
             self.stdin_channel.stop()
         if self.hb_channel.is_alive():
             self.hb_channel.stop()
 
     @property
     def channels_running(self):
         """Are any of the channels created and running?"""
         return (self.shell_channel.is_alive() or self.iopub_channel.is_alive() or
                 self.stdin_channel.is_alive() or self.hb_channel.is_alive())
 
     ioloop = None  # Overridden in subclasses that use pyzmq event loop
 
     @property
     def shell_channel(self):
         """Get the shell channel object for this kernel."""
         if self._shell_channel is None:
             url = self._make_url('shell')
             self.log.debug("connecting shell channel to %s", url)
             socket = make_shell_socket(self.context, self.session.bsession, url)
             self._shell_channel = self.shell_channel_class(
                 socket, self.session, self.ioloop
             )
         return self._shell_channel
 
     @property
     def iopub_channel(self):
         """Get the iopub channel object for this kernel."""
         if self._iopub_channel is None:
             url = self._make_url('iopub')
             self.log.debug("connecting iopub channel to %s", url)
             socket = make_iopub_socket(self.context, self.session.bsession, url)
             self._iopub_channel = self.iopub_channel_class(
                 socket, self.session, self.ioloop
             )
         return self._iopub_channel
 
     @property
     def stdin_channel(self):
         """Get the stdin channel object for this kernel."""
         if self._stdin_channel is None:
             url = self._make_url('stdin')
             self.log.debug("connecting stdin channel to %s", url)
             socket = make_stdin_socket(self.context, self.session.bsession, url)
             self._stdin_channel = self.stdin_channel_class(
                 socket, self.session, self.ioloop
             )
         return self._stdin_channel
 
     @property
     def hb_channel(self):
         """Get the hb channel object for this kernel."""
         if self._hb_channel is None:
             url = self._make_url('hb')
             self.log.debug("connecting heartbeat channel to %s", url)
             self._hb_channel = self.hb_channel_class(
                 self.context, self.session, url
             )
         return self._hb_channel
 
     def is_alive(self):
         """Is the kernel process still running?"""
         if self._hb_channel is not None:
             # We didn't start the kernel with this KernelManager so we
             # use the heartbeat.
             return self._hb_channel.is_beating()
         else:
             # no heartbeat and not local, we can't tell if it's running,
             # so naively return True
             return True
 
 
     # Methods to send specific messages on channels
     def execute(self, code, silent=False, store_history=True,
                 user_expressions=None, allow_stdin=None):
         """Execute code in the kernel.
 
         Parameters
         ----------
         code : str
             A string of Python code.
 
         silent : bool, optional (default False)
             If set, the kernel will execute the code as quietly possible, and
             will force store_history to be False.
 
         store_history : bool, optional (default True)
             If set, the kernel will store command history.  This is forced
             to be False if silent is True.
 
         user_expressions : dict, optional
             A dict mapping names to expressions to be evaluated in the user's
             dict. The expression values are returned as strings formatted using
             :func:`repr`.
 
         allow_stdin : bool, optional (default self.allow_stdin)
             Flag for whether the kernel can send stdin requests to frontends.
 
             Some frontends (e.g. the Notebook) do not support stdin requests.
             If raw_input is called from code executed from such a frontend, a
             StdinNotImplementedError will be raised.
 
         Returns
         -------
         The msg_id of the message sent.
         """
         if user_expressions is None:
             user_expressions = {}
         if allow_stdin is None:
             allow_stdin = self.allow_stdin
 
 
         # Don't waste network traffic if inputs are invalid
         if not isinstance(code, string_types):
             raise ValueError('code %r must be a string' % code)
         validate_string_dict(user_expressions)
 
         # Create class for content/msg creation. Related to, but possibly
         # not in Session.
         content = dict(code=code, silent=silent, store_history=store_history,
                        user_expressions=user_expressions,
                        allow_stdin=allow_stdin,
                        )
         msg = self.session.msg('execute_request', content)
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def complete(self, code, cursor_pos=None):
         """Tab complete text in the kernel's namespace.
 
         Parameters
         ----------
         code : str
             The context in which completion is requested.
             Can be anything between a variable name and an entire cell.
         cursor_pos : int, optional
             The position of the cursor in the block of code where the completion was requested.
             Default: ``len(code)``
 
         Returns
         -------
         The msg_id of the message sent.
         """
         if cursor_pos is None:
             cursor_pos = len(code)
         content = dict(code=code, cursor_pos=cursor_pos)
         msg = self.session.msg('complete_request', content)
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def inspect(self, code, cursor_pos=None, detail_level=0):
         """Get metadata information about an object in the kernel's namespace.
 
         It is up to the kernel to determine the appropriate object to inspect.
 
         Parameters
         ----------
         code : str
             The context in which info is requested.
             Can be anything between a variable name and an entire cell.
         cursor_pos : int, optional
             The position of the cursor in the block of code where the info was requested.
             Default: ``len(code)``
         detail_level : int, optional
             The level of detail for the introspection (0-2)
 
         Returns
         -------
         The msg_id of the message sent.
         """
         if cursor_pos is None:
             cursor_pos = len(code)
         content = dict(code=code, cursor_pos=cursor_pos,
             detail_level=detail_level,
         )
         msg = self.session.msg('inspect_request', content)
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def history(self, raw=True, output=False, hist_access_type='range', **kwargs):
         """Get entries from the kernel's history list.
 
         Parameters
         ----------
         raw : bool
             If True, return the raw input.
         output : bool
             If True, then return the output as well.
         hist_access_type : str
             'range' (fill in session, start and stop params), 'tail' (fill in n)
              or 'search' (fill in pattern param).
 
         session : int
             For a range request, the session from which to get lines. Session
             numbers are positive integers; negative ones count back from the
             current session.
         start : int
             The first line number of a history range.
         stop : int
             The final (excluded) line number of a history range.
 
         n : int
             The number of lines of history to get for a tail request.
 
         pattern : str
             The glob-syntax pattern for a search request.
 
         Returns
         -------
         The msg_id of the message sent.
         """
         content = dict(raw=raw, output=output, hist_access_type=hist_access_type,
                                                                     **kwargs)
         msg = self.session.msg('history_request', content)
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def kernel_info(self):
         """Request kernel info."""
         msg = self.session.msg('kernel_info_request')
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def _handle_kernel_info_reply(self, msg):
         """handle kernel info reply
 
         sets protocol adaptation version
         """
         adapt_version = int(msg['content']['protocol_version'].split('.')[0])
         if adapt_version != major_protocol_version:
             self.session.adapt_version = adapt_version
 
     def shutdown(self, restart=False):
         """Request an immediate kernel shutdown.
 
         Upon receipt of the (empty) reply, client code can safely assume that
         the kernel has shut down and it's safe to forcefully terminate it if
         it's still alive.
 
         The kernel will send the reply via a function registered with Python's
         atexit module, ensuring it's truly done as the kernel is done with all
         normal operation.
         """
         # Send quit message to kernel. Once we implement kernel-side setattr,
         # this should probably be done that way, but for now this will do.
         msg = self.session.msg('shutdown_request', {'restart':restart})
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     def is_complete(self, code):
         msg = self.session.msg('is_complete_request', {'code': code})
         self.shell_channel._queue_send(msg)
         return msg['header']['msg_id']
 
     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.stdin_channel._queue_send(msg)
 
 
 KernelClientABC.register(KernelClient)

IPython/qt/client.py

@@ -1,267 +1,250
 """ Defines a KernelClient that provides signals and slots.
 """
 import atexit
 import errno
 from threading import Thread
 import time
 
 import zmq
 # import ZMQError in top-level namespace, to avoid ugly attribute-error messages
 # during garbage collection of threads at exit:
 from zmq import ZMQError
 from zmq.eventloop import ioloop, zmqstream
 
 from IPython.external.qt import QtCore
 
 # Local imports
 from IPython.utils.traitlets import Type, Instance
 from IPython.kernel.channels import HBChannel,\
     make_shell_socket, make_iopub_socket, make_stdin_socket
 from IPython.kernel import KernelClient
 
 from .kernel_mixins import QtKernelClientMixin
 from .util import SuperQObject
 
 class QtHBChannel(SuperQObject, HBChannel):
     # A longer timeout than the base class
     time_to_dead = 3.0
 
     # Emitted when the kernel has died.
     kernel_died = QtCore.Signal(object)
 
     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)
 
 from IPython.core.release import kernel_protocol_version_info
 
-from IPython.utils.py3compat import string_types, iteritems
-
 major_protocol_version = kernel_protocol_version_info[0]
 
 class InvalidPortNumber(Exception):
     pass
 
-# some utilities to validate message structure, these might get moved elsewhere
-# if they prove to have more generic utility
-
-
-def validate_string_dict(dct):
-    """Validate that the input is a dict with string keys and values.
-
-    Raises ValueError if not."""
-    for k,v in iteritems(dct):
-        if not isinstance(k, string_types):
-            raise ValueError('key %r in dict must be a string' % k)
-        if not isinstance(v, string_types):
-            raise ValueError('value %r in dict must be a string' % v)
-
-
 
 class QtZMQSocketChannel(SuperQObject):
     """A ZMQ socket emitting a Qt signal when a message is received."""
     session = None
     socket = None
     ioloop = None
     stream = None
 
     message_received = QtCore.Signal(object)
 
     def process_events(self):
         """ Process any pending GUI events.
         """
         QtCore.QCoreApplication.instance().processEvents()
 
     def __init__(self, socket, session, loop):
         """Create a channel.
 
         Parameters
         ----------
         socket : :class:`zmq.Socket`
             The ZMQ socket to use.
         session : :class:`session.Session`
             The session to use.
         loop
             A pyzmq ioloop to connect the socket to using a ZMQStream
         """
         super(QtZMQSocketChannel, self).__init__()
 
         self.socket = socket
         self.session = session
         self.ioloop = loop
 
         self.stream = zmqstream.ZMQStream(self.socket, self.ioloop)
         self.stream.on_recv(self._handle_recv)
 
     _is_alive = False
     def is_alive(self):
         return self._is_alive
 
     def start(self):
         self._is_alive = True
 
     def stop(self):
         self._is_alive = False
 
     def close(self):
         if self.socket is not None:
             try:
                 self.socket.close(linger=0)
             except Exception:
                 pass
             self.socket = None
 
     def _queue_send(self, msg):
         """Queue a message to be sent from the IOLoop's thread.
 
         Parameters
         ----------
         msg : message to send
 
         This is threadsafe, as it uses IOLoop.add_callback to give the loop's
         thread control of the action.
         """
         def thread_send():
             self.session.send(self.stream, msg)
         self.ioloop.add_callback(thread_send)
 
     def _handle_recv(self, msg):
         """Callback for stream.on_recv.
 
         Unpacks message, and calls handlers with it.
         """
         ident,smsg = self.session.feed_identities(msg)
         msg = self.session.deserialize(smsg)
         self.call_handlers(msg)
 
     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 level
         handlers are called in the application thread.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
 
     def flush(self, timeout=1.0):
         """Immediately processes all pending messages on this channel.
 
         This is only used for the IOPub channel.
 
         Callers should use this method to ensure that :meth:`call_handlers`
         has been called for all messages that have been received on the
         0MQ SUB socket of this 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 range(2):
             self._flushed = False
             self.ioloop.add_callback(self._flush)
             while not self._flushed and time.time() < stop_time:
                 time.sleep(0.01)
 
     def _flush(self):
         """Callback for :method:`self.flush`."""
         self.stream.flush()
         self._flushed = True
 
 
 class IOLoopThread(Thread):
     """Run a pyzmq ioloop in a thread to send and receive messages
     """
     def __init__(self, loop):
         super(IOLoopThread, self).__init__()
         self.daemon = True
         atexit.register(self._notice_exit)
         self.ioloop = loop or ioloop.IOLoop()
 
     def _notice_exit(self):
         self._exiting = True
 
     def run(self):
         """Run my loop, ignoring EINTR events in the poller"""
         while True:
             try:
                 self.ioloop.start()
             except ZMQError as e:
                 if e.errno == errno.EINTR:
                     continue
                 else:
                     raise
             except Exception:
                 if self._exiting:
                     break
                 else:
                     raise
             else:
                 break
 
     def stop(self):
         """Stop the channel's event loop and join its thread.
 
         This calls :meth:`~threading.Thread.join` and returns when the thread
         terminates. :class:`RuntimeError` will be raised if
         :meth:`~threading.Thread.start` is called again.
         """
         if self.ioloop is not None:
             self.ioloop.stop()
         self.join()
         self.close()
 
     def close(self):
         if self.ioloop is not None:
             try:
                 self.ioloop.close(all_fds=True)
             except Exception:
                 pass
 
 
 class QtKernelClient(QtKernelClientMixin, KernelClient):
     """ A KernelClient that provides signals and slots.
     """
 
     _ioloop = None
     @property
     def ioloop(self):
         if self._ioloop is None:
             self._ioloop = ioloop.IOLoop()
         return self._ioloop
 
     ioloop_thread = Instance(IOLoopThread)
 
     def start_channels(self, shell=True, iopub=True, stdin=True, hb=True):
         if shell:
             self.shell_channel.message_received.connect(self._check_kernel_info_reply)
 
         self.ioloop_thread = IOLoopThread(self.ioloop)
         self.ioloop_thread.start()
 
         super(QtKernelClient, self).start_channels(shell, iopub, stdin, hb)
 
     def _check_kernel_info_reply(self, msg):
         if msg['msg_type'] == 'kernel_info_reply':
             self._handle_kernel_info_reply(msg)
             self.shell_channel.message_received.disconnect(self._check_kernel_info_reply)
 
     def stop_channels(self):
         super(QtKernelClient, self).stop_channels()
         if self.ioloop_thread.is_alive():
             self.ioloop_thread.stop()
 
     iopub_channel_class = Type(QtZMQSocketChannel)
     shell_channel_class = Type(QtZMQSocketChannel)
     stdin_channel_class = Type(QtZMQSocketChannel)
     hb_channel_class = Type(QtHBChannel)