Source code for holoviews.plotting.comms

import json
import uuid
import sys
import traceback
    from StringIO import StringIO
    from io import StringIO

from ipykernel.comm import Comm as IPyComm
from IPython import get_ipython

[docs]class StandardOutput(list): """ Context manager to capture standard output for any code it is wrapping and make it available as a list, e.g.: >>> with StandardOutput() as stdout: ... print('This gets captured') >>> print(stdout[0]) This gets captured """ def __enter__(self): self._stdout = sys.stdout sys.stdout = self._stringio = StringIO() return self def __exit__(self, *args): self.extend(self._stringio.getvalue().splitlines()) sys.stdout = self._stdout
[docs]class Comm(object): """ Comm encompasses any uni- or bi-directional connection between a python process and a frontend allowing passing of messages between the two. A Comms class must implement methods send data and handle received message events. If the Comm has to be set up on the frontend a template to handle the creation of the comms channel along with a message handler to process incoming messages must be supplied. The template must accept three arguments: * id - A unique id to register to register the comm under. * msg_handler - JS code which has the msg variable in scope and performs appropriate action for the supplied message. * init_frame - The initial frame to render on the frontend. """ template = '' def __init__(self, plot, id=None, on_msg=None): """ Initializes a Comms object """ = id if id else uuid.uuid4().hex self._plot = plot self._on_msg = on_msg self._comm = None
[docs] def init(self, on_msg=None): """ Initializes comms channel. """
[docs] def send(self, data): """ Sends data to the frontend """
[docs] def decode(cls, msg): """ Decode incoming message, e.g. by parsing json. """ return msg
@property def comm(self): if not self._comm: raise ValueError('Comm has not been initialized') return self._comm def _handle_msg(self, msg): """ Decode received message before passing it to on_msg callback if it has been defined. """ comm_id = None try: stdout = [] msg = self.decode(msg) comm_id = msg.pop('comm_id', None) if self._on_msg: # Comm swallows standard output so we need to capture # it and then send it to the frontend with StandardOutput() as stdout: self._on_msg(msg) except Exception as e: frame =traceback.extract_tb(sys.exc_info()[2])[-2] fname,lineno,fn,text = frame error_kwargs = dict(type=type(e).__name__, fn=fn, fname=fname, line=lineno, error=str(e)) error = '{fname} {fn} L{line}\n\t{type}: {error}'.format(**error_kwargs) if stdout: stdout = '\n\t'+'\n\t'.join(stdout) error = '\n'.join([stdout, error]) reply = {'msg_type': "Error", 'traceback': error} else: stdout = '\n\t'+'\n\t'.join(stdout) if stdout else '' reply = {'msg_type': "Ready", 'content': stdout} # Returning the comm_id in an ACK message ensures that # the correct comms handle is unblocked if comm_id: reply['comm_id'] = comm_id self.send(json.dumps(reply))
[docs]class JupyterComm(Comm): """ JupyterComm provides a Comm for the notebook which is initialized the first time data is pushed to the frontend. """ template = """ <script> function msg_handler(msg) {{ var msg =; {msg_handler} }} if ((window.Jupyter !== undefined) && (Jupyter.notebook.kernel != null)) {{ comm_manager = Jupyter.notebook.kernel.comm_manager; comm_manager.register_target("{comm_id}", function(comm) {{ comm.on_msg(msg_handler);}}); }} </script> <div id="fig_{comm_id}"> {init_frame} </div> """ def init(self): if self._comm: return self._comm = IPyComm(, data={}) self._comm.on_msg(self._handle_msg) @classmethod
[docs] def decode(cls, msg): """ Decodes messages following Jupyter messaging protocol. If JSON decoding fails data is assumed to be a regular string. """ return msg['content']['data']
[docs] def send(self, data): """ Pushes data across comm socket. """ if not self._comm: self.init() self.comm.send(data)
[docs]class JupyterCommJS(JupyterComm): """ JupyterCommJS provides a comms channel for the Jupyter notebook, which is initialized on the frontend. This allows sending events initiated on the frontend to python. """ template = """ <script> function msg_handler(msg) {{ var msg =; {msg_handler} }} if ((window.Jupyter !== undefined) && (Jupyter.notebook.kernel != null)) {{ var comm_manager = Jupyter.notebook.kernel.comm_manager; comm = comm_manager.new_comm("{comm_id}", {{}}, {{}}, {{}}, "{comm_id}"); comm.on_msg(msg_handler); }} </script> <div id="fig_{comm_id}"> {init_frame} </div> """ def __init__(self, plot, id=None, on_msg=None): """ Initializes a Comms object """ super(JupyterCommJS, self).__init__(plot, id, on_msg) self.manager = get_ipython().kernel.comm_manager self.manager.register_target(, self._handle_open) def _handle_open(self, comm, msg): self._comm = comm self._comm.on_msg(self._handle_msg)
[docs] def send(self, data): """ Pushes data across comm socket. """ self.comm.send(data)