displayhook.py

"""Replacements for sys.displayhook that publish over ZMQ."""

# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.

import builtins
import sys

from IPython.core.displayhook import DisplayHook
from ipykernel.jsonutil import encode_images, json_clean
from traitlets import Instance, Dict, Any
from jupyter_client.session import extract_header, Session


class ZMQDisplayHook:
    """A simple displayhook that publishes the object's repr over a ZeroMQ
    socket."""
    topic = b'execute_result'

    def __init__(self, session, pub_socket):
        self.session = session
        self.pub_socket = pub_socket
        self.parent_header = {}

    def get_execution_count(self):
        """This method is replaced in kernelapp"""
        return 0

    def __call__(self, obj):
        if obj is None:
            return

        builtins._ = obj
        sys.stdout.flush()
        sys.stderr.flush()
        contents = {'execution_count': self.get_execution_count(),
                    'data': {'text/plain': repr(obj)},
                    'metadata': {}}
        self.session.send(self.pub_socket, 'execute_result', contents,
                          parent=self.parent_header, ident=self.topic)

    def set_parent(self, parent):
        self.parent_header = extract_header(parent)


class ZMQShellDisplayHook(DisplayHook):
    """A displayhook subclass that publishes data using ZeroMQ. This is intended
    to work with an InteractiveShell instance. It sends a dict of different
    representations of the object."""
    topic=None

    session = Instance(Session, allow_none=True)
    pub_socket = Any(allow_none=True)
    parent_header = Dict({})

    def set_parent(self, parent):
        """Set the parent for outbound messages."""
        self.parent_header = extract_header(parent)

    def start_displayhook(self):
        self.msg = self.session.msg('execute_result', {
            'data': {},
            'metadata': {},
        }, parent=self.parent_header)

    def write_output_prompt(self):
        """Write the output prompt."""
        self.msg['content']['execution_count'] = self.prompt_count

    def write_format_data(self, format_dict, md_dict=None):
        self.msg['content']['data'] = json_clean(encode_images(format_dict))
        self.msg['content']['metadata'] = md_dict

    def finish_displayhook(self):
        """Finish up all displayhook activities."""
        sys.stdout.flush()
        sys.stderr.flush()
        if self.msg['content']['data']:
            self.session.send(self.pub_socket, self.msg, ident=self.topic)
        self.msg = None