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Fix race condition in javascript kernel message processing...
Fix race condition in javascript kernel message processing Because the binary messages are now deserialized using the asynchronous FileReader API, we need to have some way to force the messages to still be processed in the order they are received. This patch implements a simple processing queue using promises.

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widget_output.py
78 lines | 2.7 KiB | text/x-python | PythonLexer
"""Output class.
Represents a widget that can be used to display output within the widget area.
"""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
from .widget import DOMWidget
import sys
from IPython.utils.traitlets import Unicode, List
from IPython.display import clear_output
from IPython.testing.skipdoctest import skip_doctest
from IPython.kernel.zmq.session import Message
@skip_doctest
class Output(DOMWidget):
"""Widget used as a context manager to display output.
This widget can capture and display stdout, stderr, and rich output. To use
it, create an instance of it and display it. Then use it as a context
manager. Any output produced while in it's context will be captured and
displayed in it instead of the standard output area.
Example
from IPython.html import widgets
from IPython.display import display
out = widgets.Output()
display(out)
print('prints to output area')
with out:
print('prints to output widget')"""
_view_name = Unicode('OutputView', sync=True)
def clear_output(self, *pargs, **kwargs):
with self:
clear_output(*pargs, **kwargs)
def __enter__(self):
"""Called upon entering output widget context manager."""
self._flush()
kernel = get_ipython().kernel
session = kernel.session
send = session.send
self._original_send = send
self._session = session
def send_hook(stream, msg_or_type, content=None, parent=None, ident=None,
buffers=None, track=False, header=None, metadata=None):
# Handle both prebuild messages and unbuilt messages.
if isinstance(msg_or_type, (Message, dict)):
msg_type = msg_or_type['msg_type']
msg = dict(msg_or_type)
else:
msg_type = msg_or_type
msg = session.msg(msg_type, content=content, parent=parent,
header=header, metadata=metadata)
# If this is a message type that we want to forward, forward it.
if stream is kernel.iopub_socket and msg_type in ['clear_output', 'stream', 'display_data']:
self.send(msg)
else:
send(stream, msg, ident=ident, buffers=buffers, track=track)
session.send = send_hook
def __exit__(self, exception_type, exception_value, traceback):
"""Called upon exiting output widget context manager."""
self._flush()
self._session.send = self._original_send
def _flush(self):
"""Flush stdout and stderr buffers."""
sys.stdout.flush()
sys.stderr.flush()