How to use the qtconsole.qt.QtCore.Signal function in qtconsole

import re

from qtconsole.qt import QtGui,QtCore


class MagicHelper(QtGui.QDockWidget):
    """MagicHelper - dockable widget for convenient search and running of
                     magic command for Jupyter QtConsole.
    """

    #---------------------------------------------------------------------------
    # signals
    #---------------------------------------------------------------------------

    pasteRequested = QtCore.Signal(str, name = 'pasteRequested')
    """This signal is emitted when user wants to paste selected magic 
       command into the command line.
    """

    runRequested = QtCore.Signal(str, name = 'runRequested')
    """This signal is emitted when user wants to execute selected magic command
    """

    readyForUpdate = QtCore.Signal(name = 'readyForUpdate')
    """This signal is emitted when MagicHelper is ready to be populated.
       Since kernel querying mechanisms are out of scope of this class,
       it expects its owner to invoke MagicHelper.populate_magic_helper()
       as a reaction on this event.
    """

    #---------------------------------------------------------------------------

comm_id = content['comm_id']
        comm = self.get_comm(comm_id)
        if comm is None:
            return
        try:
            comm.handle_msg(msg)
        except Exception:
            self.log.error('Exception in comm_msg for %s', comm_id,
                           exc_info=True)

class Comm(MetaQObjectHasTraits(
        'NewBase', (LoggingConfigurable, SuperQObject), {})):
    """
    Comm base class
    """
    sig_is_closing = QtCore.Signal(object)

    def __init__(self, target_name, kernel_client, comm_id=None,
                 msg_callback=None, close_callback=None):
        """
        Create a new comm. Must call open to use.
        """
        super(Comm, self).__init__(target_name=target_name)
        self.target_name = target_name
        self.kernel_client = kernel_client
        if comm_id is None:
            comm_id = uuid.uuid1().hex
        self.comm_id = comm_id
        self._msg_callback = msg_callback
        self._close_callback = close_callback
        self._send_channel = self.kernel_client.shell_channel

custom_control = None
    custom_page_control = None

    #------ Signals ------------------------------------------------------------

    # Signals that indicate ConsoleWidget state.
    copy_available = QtCore.Signal(bool)
    redo_available = QtCore.Signal(bool)
    undo_available = QtCore.Signal(bool)

    # Signal emitted when paging is needed and the paging style has been
    # specified as 'custom'.
    custom_page_requested = QtCore.Signal(object)

    # Signal emitted when the font is changed.
    font_changed = QtCore.Signal(QtGui.QFont)

    #------ Protected class variables ------------------------------------------

    # control handles
    _control = None
    _page_control = None
    _splitter = None

    # When the control key is down, these keys are mapped.
    _ctrl_down_remap = { QtCore.Qt.Key_B : QtCore.Qt.Key_Left,
                         QtCore.Qt.Key_F : QtCore.Qt.Key_Right,
                         QtCore.Qt.Key_A : QtCore.Qt.Key_Home,
                         QtCore.Qt.Key_P : QtCore.Qt.Key_Up,
                         QtCore.Qt.Key_N : QtCore.Qt.Key_Down,
                         QtCore.Qt.Key_H : QtCore.Qt.Key_Backspace, }
    if not sys.platform == 'darwin':

self.lexer = lexer_class()

    def _lexer_class_default(self):
        if py3compat.PY3:
            return 'pygments.lexers.Python3Lexer'
        else:
            return 'pygments.lexers.PythonLexer'

    lexer = Any()
    def _lexer_default(self):
        lexer_class = import_item(self.lexer_class)
        return lexer_class()

    # Emitted when a user visible 'execute_request' has been submitted to the
    # kernel from the FrontendWidget. Contains the code to be executed.
    executing = QtCore.Signal(object)

    # Emitted when a user-visible 'execute_reply' has been received from the
    # kernel and processed by the FrontendWidget. Contains the response message.
    executed = QtCore.Signal(object)

    # Emitted when an exit request has been received from the kernel.
    exit_requested = QtCore.Signal(object)

    _CallTipRequest = namedtuple('_CallTipRequest', ['id', 'pos'])
    _CompletionRequest = namedtuple('_CompletionRequest', ['id', 'pos'])
    _ExecutionRequest = namedtuple('_ExecutionRequest', ['id', 'kind'])
    _local_kernel = False
    _highlighter = Instance(FrontendHighlighter, allow_none=True)

    # -------------------------------------------------------------------------
    # 'Object' interface

# The text to show when the kernel is (re)started.
    banner = Unicode(config=True)
    kernel_banner = Unicode()
    # Whether to show the banner
    _display_banner = Bool(False)

    # An option and corresponding signal for overriding the default kernel
    # interrupt behavior.
    custom_interrupt = Bool(False)
    custom_interrupt_requested = QtCore.Signal()

    # An option and corresponding signals for overriding the default kernel
    # restart behavior.
    custom_restart = Bool(False)
    custom_restart_kernel_died = QtCore.Signal(float)
    custom_restart_requested = QtCore.Signal()

    # Whether to automatically show calltips on open-parentheses.
    enable_calltips = Bool(True, config=True,
        help="Whether to draw information calltips on open-parentheses.")

    clear_on_kernel_restart = Bool(True, config=True,
        help="Whether to clear the console when the kernel is restarted")

    confirm_restart = Bool(True, config=True,
        help="Whether to ask for user confirmation when restarting kernel")

    lexer_class = DottedObjectName(config=True,
        help="The pygments lexer class to use."
    )
    def _lexer_class_changed(self, name, old, new):
        lexer_class = import_item(new)

# For other projects to easily override the Qt widgets used by the console
    # (e.g. Spyder)
    custom_control = None
    custom_page_control = None

    #------ Signals ------------------------------------------------------------

    # Signals that indicate ConsoleWidget state.
    copy_available = QtCore.Signal(bool)
    redo_available = QtCore.Signal(bool)
    undo_available = QtCore.Signal(bool)

    # Signal emitted when paging is needed and the paging style has been
    # specified as 'custom'.
    custom_page_requested = QtCore.Signal(object)

    # Signal emitted when the font is changed.
    font_changed = QtCore.Signal(QtGui.QFont)

    #------ Protected class variables ------------------------------------------

    # control handles
    _control = None
    _page_control = None
    _splitter = None

    # When the control key is down, these keys are mapped.
    _ctrl_down_remap = { QtCore.Qt.Key_B : QtCore.Qt.Key_Left,
                         QtCore.Qt.Key_F : QtCore.Qt.Key_Right,
                         QtCore.Qt.Key_A : QtCore.Qt.Key_Home,
                         QtCore.Qt.Key_P : QtCore.Qt.Key_Up,

# priority (when it has focus) over, e.g., window-level menu shortcuts.
    override_shortcuts = Bool(False)
    
    # ------ Custom Qt Widgets -------------------------------------------------
    
    # For other projects to easily override the Qt widgets used by the console
    # (e.g. Spyder)
    custom_control = None
    custom_page_control = None

    #------ Signals ------------------------------------------------------------

    # Signals that indicate ConsoleWidget state.
    copy_available = QtCore.Signal(bool)
    redo_available = QtCore.Signal(bool)
    undo_available = QtCore.Signal(bool)

    # Signal emitted when paging is needed and the paging style has been
    # specified as 'custom'.
    custom_page_requested = QtCore.Signal(object)

    # Signal emitted when the font is changed.
    font_changed = QtCore.Signal(QtGui.QFont)

    #------ Protected class variables ------------------------------------------

    # control handles
    _control = None
    _page_control = None
    _splitter = None

    # When the control key is down, these keys are mapped.

# widget (Ctrl+n, Ctrl+a, etc). Enable this if you want this widget to take
    # priority (when it has focus) over, e.g., window-level menu shortcuts.
    override_shortcuts = Bool(False)
    
    # ------ Custom Qt Widgets -------------------------------------------------
    
    # For other projects to easily override the Qt widgets used by the console
    # (e.g. Spyder)
    custom_control = None
    custom_page_control = None

    #------ Signals ------------------------------------------------------------

    # Signals that indicate ConsoleWidget state.
    copy_available = QtCore.Signal(bool)
    redo_available = QtCore.Signal(bool)
    undo_available = QtCore.Signal(bool)

    # Signal emitted when paging is needed and the paging style has been
    # specified as 'custom'.
    custom_page_requested = QtCore.Signal(object)

    # Signal emitted when the font is changed.
    font_changed = QtCore.Signal(QtGui.QFont)

    #------ Protected class variables ------------------------------------------

    # control handles
    _control = None
    _page_control = None
    _splitter = None

class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):
    """ A Qt frontend for a generic Python kernel.
    """

    # The text to show when the kernel is (re)started.
    banner = Unicode(config=True)
    kernel_banner = Unicode()
    # Whether to show the banner
    _display_banner = Bool(False)

    # An option and corresponding signal for overriding the default kernel
    # interrupt behavior.
    custom_interrupt = Bool(False)
    custom_interrupt_requested = QtCore.Signal()

    # An option and corresponding signals for overriding the default kernel
    # restart behavior.
    custom_restart = Bool(False)
    custom_restart_kernel_died = QtCore.Signal(float)
    custom_restart_requested = QtCore.Signal()

    # Whether to automatically show calltips on open-parentheses.
    enable_calltips = Bool(True, config=True,
        help="Whether to draw information calltips on open-parentheses.")

    clear_on_kernel_restart = Bool(True, config=True,
        help="Whether to clear the console when the kernel is restarted")

    confirm_restart = Bool(True, config=True,
        help="Whether to ask for user confirmation when restarting kernel")