intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 131 insertions, 0 deletions

diff --git a/contrib/python/ipython/py2/IPython/core/events.py b/contrib/python/ipython/py2/IPython/core/events.py
new file mode 100644
index 0000000000..bfd09fec6a
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/core/events.py
@@ -0,0 +1,131 @@
+"""Infrastructure for registering and firing callbacks on application events.
+
+Unlike :mod:`IPython.core.hooks`, which lets end users set single functions to
+be called at specific times, or a collection of alternative methods to try,
+callbacks are designed to be used by extension authors. A number of callbacks
+can be registered for the same event without needing to be aware of one another.
+
+The functions defined in this module are no-ops indicating the names of available
+events and the arguments which will be passed to them.
+
+.. note::
+
+   This API is experimental in IPython 2.0, and may be revised in future versions.
+"""
+from __future__ import print_function
+
+class EventManager(object):
+    """Manage a collection of events and a sequence of callbacks for each.
+    
+    This is attached to :class:`~IPython.core.interactiveshell.InteractiveShell`
+    instances as an ``events`` attribute.
+    
+    .. note::
+
+       This API is experimental in IPython 2.0, and may be revised in future versions.
+    """
+    def __init__(self, shell, available_events):
+        """Initialise the :class:`CallbackManager`.
+        
+        Parameters
+        ----------
+        shell
+          The :class:`~IPython.core.interactiveshell.InteractiveShell` instance
+        available_callbacks
+          An iterable of names for callback events.
+        """
+        self.shell = shell
+        self.callbacks = {n:[] for n in available_events}
+    
+    def register(self, event, function):
+        """Register a new event callback
+        
+        Parameters
+        ----------
+        event : str
+          The event for which to register this callback.
+        function : callable
+          A function to be called on the given event. It should take the same
+          parameters as the appropriate callback prototype.
+        
+        Raises
+        ------
+        TypeError
+          If ``function`` is not callable.
+        KeyError
+          If ``event`` is not one of the known events.
+        """
+        if not callable(function):
+            raise TypeError('Need a callable, got %r' % function)
+        self.callbacks[event].append(function)
+    
+    def unregister(self, event, function):
+        """Remove a callback from the given event."""
+        self.callbacks[event].remove(function)
+    
+    def trigger(self, event, *args, **kwargs):
+        """Call callbacks for ``event``.
+        
+        Any additional arguments are passed to all callbacks registered for this
+        event. Exceptions raised by callbacks are caught, and a message printed.
+        """
+        for func in self.callbacks[event][:]:
+            try:
+                func(*args, **kwargs)
+            except Exception:
+                print("Error in callback {} (for {}):".format(func, event))
+                self.shell.showtraceback()
+
+# event_name -> prototype mapping
+available_events = {}
+
+def _define_event(callback_proto):
+    available_events[callback_proto.__name__] = callback_proto
+    return callback_proto
+
+# ------------------------------------------------------------------------------
+# Callback prototypes
+#
+# No-op functions which describe the names of available events and the
+# signatures of callbacks for those events.
+# ------------------------------------------------------------------------------
+
+@_define_event
+def pre_execute():
+    """Fires before code is executed in response to user/frontend action.
+    
+    This includes comm and widget messages and silent execution, as well as user
+    code cells."""
+    pass
+
+@_define_event
+def pre_run_cell():
+    """Fires before user-entered code runs."""
+    pass
+
+@_define_event
+def post_execute():
+    """Fires after code is executed in response to user/frontend action.
+    
+    This includes comm and widget messages and silent execution, as well as user
+    code cells."""
+    pass
+
+@_define_event
+def post_run_cell():
+    """Fires after user-entered code runs."""
+    pass
+
+@_define_event
+def shell_initialized(ip):
+    """Fires after initialisation of :class:`~IPython.core.interactiveshell.InteractiveShell`.
+    
+    This is before extensions and startup scripts are loaded, so it can only be
+    set by subclassing.
+    
+    Parameters
+    ----------
+    ip : :class:`~IPython.core.interactiveshell.InteractiveShell`
+      The newly initialised shell.
+    """
+    pass