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"""Output class.
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Represents a widget that can be used to display output within the widget area.
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"""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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from .widget import DOMWidget
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import sys
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from IPython.utils.traitlets import Unicode, List
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from IPython.display import clear_output
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from IPython.testing.skipdoctest import skip_doctest
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from IPython.kernel.zmq.session import Message
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@skip_doctest
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class Output(DOMWidget):
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"""Widget used as a context manager to display output.
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This widget can capture and display stdout, stderr, and rich output. To use
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it, create an instance of it and display it. Then use it as a context
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manager. Any output produced while in it's context will be captured and
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displayed in it instead of the standard output area.
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Example
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from IPython.html import widgets
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from IPython.display import display
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out = widgets.Output()
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display(out)
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print('prints to output area')
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with out:
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print('prints to output widget')"""
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_view_name = Unicode('OutputView', sync=True)
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def __init__(self, *args, **kwargs):
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super(Output, self).__init__(*args, **kwargs)
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from IPython import get_ipython
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ip = get_ipython()
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if ip is not None and hasattr(ip, 'kernel'):
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self._kernel = ip.kernel
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else:
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self._kernel = None
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def clear_output(self, *pargs, **kwargs):
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with self:
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clear_output(*pargs, **kwargs)
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def __enter__(self):
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"""Called upon entering output widget context manager."""
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if self._kernel is not None:
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self._flush()
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session = self._kernel.session
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send = session.send
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self._original_send = send
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self._session = session
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def send_hook(stream, msg_or_type, content=None, parent=None, ident=None,
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buffers=None, track=False, header=None, metadata=None):
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# Handle both prebuild messages and unbuilt messages.
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if isinstance(msg_or_type, (Message, dict)):
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msg_type = msg_or_type['msg_type']
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msg = dict(msg_or_type)
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else:
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msg_type = msg_or_type
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msg = session.msg(msg_type, content=content, parent=parent,
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header=header, metadata=metadata)
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# If this is a message type that we want to forward, forward it.
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if stream is self._kernel.iopub_socket and msg_type in ['clear_output', 'stream', 'display_data']:
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self.send(msg)
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else:
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send(stream, msg, ident=ident, buffers=buffers, track=track)
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session.send = send_hook
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def __exit__(self, exception_type, exception_value, traceback):
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"""Called upon exiting output widget context manager."""
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if self._kernel is not None:
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self._flush()
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self._session.send = self._original_send
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def _flush(self):
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"""Flush stdout and stderr buffers."""
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sys.stdout.flush()
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sys.stderr.flush()
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