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""" Defines a convenient mix-in class for implementing Qt frontends.
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"""
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class BaseFrontendMixin(object):
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""" A mix-in class for implementing Qt frontends.
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To handle messages of a particular type, frontends need only define an
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appropriate handler method. For example, to handle 'stream' messaged, define
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a '_handle_stream(msg)' method.
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"""
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#---------------------------------------------------------------------------
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# 'BaseFrontendMixin' concrete interface
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#---------------------------------------------------------------------------
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def _get_kernel_manager(self):
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""" Returns the current kernel manager.
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"""
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return self._kernel_manager
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def _set_kernel_manager(self, kernel_manager):
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""" Disconnect from the current kernel manager (if any) and set a new
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kernel manager.
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"""
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# Disconnect the old kernel manager, if necessary.
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old_manager = self._kernel_manager
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if old_manager is not None:
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old_manager.started_kernel.disconnect(self._started_kernel)
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old_manager.started_channels.disconnect(self._started_channels)
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old_manager.stopped_channels.disconnect(self._stopped_channels)
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# Disconnect the old kernel manager's channels.
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old_manager.sub_channel.message_received.disconnect(self._dispatch)
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old_manager.shell_channel.message_received.disconnect(self._dispatch)
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old_manager.stdin_channel.message_received.disconnect(self._dispatch)
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old_manager.hb_channel.kernel_died.disconnect(
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self._handle_kernel_died)
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# Handle the case where the old kernel manager is still listening.
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if old_manager.channels_running:
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self._stopped_channels()
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# Set the new kernel manager.
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self._kernel_manager = kernel_manager
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if kernel_manager is None:
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return
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# Connect the new kernel manager.
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kernel_manager.started_kernel.connect(self._started_kernel)
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kernel_manager.started_channels.connect(self._started_channels)
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kernel_manager.stopped_channels.connect(self._stopped_channels)
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# Connect the new kernel manager's channels.
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kernel_manager.sub_channel.message_received.connect(self._dispatch)
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kernel_manager.shell_channel.message_received.connect(self._dispatch)
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kernel_manager.stdin_channel.message_received.connect(self._dispatch)
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kernel_manager.hb_channel.kernel_died.connect(self._handle_kernel_died)
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# Handle the case where the kernel manager started channels before
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# we connected.
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if kernel_manager.channels_running:
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self._started_channels()
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kernel_manager = property(_get_kernel_manager, _set_kernel_manager)
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#---------------------------------------------------------------------------
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# 'BaseFrontendMixin' abstract interface
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#---------------------------------------------------------------------------
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def _handle_kernel_died(self, since_last_heartbeat):
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""" This is called when the ``kernel_died`` signal is emitted.
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This method is called when the kernel heartbeat has not been
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active for a certain amount of time. The typical action will be to
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give the user the option of restarting the kernel.
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Parameters
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----------
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since_last_heartbeat : float
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The time since the heartbeat was last received.
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"""
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def _started_kernel(self):
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"""Called when the KernelManager starts (or restarts) the kernel subprocess.
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Channels may or may not be running at this point.
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"""
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def _started_channels(self):
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""" Called when the KernelManager channels have started listening or
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when the frontend is assigned an already listening KernelManager.
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"""
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def _stopped_channels(self):
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""" Called when the KernelManager channels have stopped listening or
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when a listening KernelManager is removed from the frontend.
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"""
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#---------------------------------------------------------------------------
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# 'BaseFrontendMixin' protected interface
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#---------------------------------------------------------------------------
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def _dispatch(self, msg):
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""" Calls the frontend handler associated with the message type of the
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given message.
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"""
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msg_type = msg['header']['msg_type']
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handler = getattr(self, '_handle_' + msg_type, None)
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if handler:
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handler(msg)
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def _is_from_this_session(self, msg):
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""" Returns whether a reply from the kernel originated from a request
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from this frontend.
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"""
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session = self._kernel_manager.session.session
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parent = msg['parent_header']
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if not parent:
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# if the message has no parent, assume it is meant for all frontends
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return True
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else:
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return parent.get('session') == session
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