#----------------------------------------------------------------------------- # Copyright (c) 2012 - 2020, Anaconda, Inc., and Bokeh Contributors. # All rights reserved. # # The full license is in the file LICENSE.txt, distributed with this software. #----------------------------------------------------------------------------- ''' Provide a Bokeh Application Handler to build up documents by running a specified Python function. This Handler is not used by the Bokeh server command line tool, but is often useful if users wish to embed the Bokeh server programmatically: .. code-block:: python def make_doc(doc): # do work to modify the document, add plots, widgets, etc. return doc app = Application(FunctionHandler(make_doc)) server = Server({'/bkapp': app}, io_loop=IOLoop.current()) server.start() For complete examples of this technique, see :bokeh-tree:`examples/howto/server_embed` ''' #----------------------------------------------------------------------------- # Boilerplate #----------------------------------------------------------------------------- import logging # isort:skip log = logging.getLogger(__name__) #----------------------------------------------------------------------------- # Imports #----------------------------------------------------------------------------- # Bokeh imports from ...util.callback_manager import _check_callback from .handler import Handler, handle_exception #----------------------------------------------------------------------------- # Globals and constants #----------------------------------------------------------------------------- __all__ = ( 'FunctionHandler', ) #----------------------------------------------------------------------------- # General API #----------------------------------------------------------------------------- #----------------------------------------------------------------------------- # Dev API #----------------------------------------------------------------------------- [docs]class FunctionHandler(Handler): ''' A Handler that accepts a plain python function to use for modifying Bokeh Documents. For example, the following code configures a handler with a function that adds an empty plot to a Document: .. code-block:: python def add_empty_plot(doc): p = figure(x_range=(0,10), y_range=(0, 10)) doc.add_root(p) return doc handler = FunctionHandler(add_empty_plot) This handler could be configured on an Application, and the Application would run this function every time a new session is created. ''' [docs] def __init__(self, func, *, trap_exceptions=False): ''' Args: func (callable) : a function to modify and return a Bokeh Document. The function should have the form: .. code-block:: python def func(doc): # modify doc return doc and it should return the passed-in document after making any modifications in-place. trap_exceptions (bool) : should exceptions in `func` be caught and logged or allowed to propagate ''' super().__init__() _check_callback(func, ('doc',)) self._func = func self._trap_exceptions = trap_exceptions self._safe_to_fork = True # Properties -------------------------------------------------------------- @property def safe_to_fork(self): ''' Whether it is still safe for the Bokeh server to fork new workers. ``False`` if ``modify_doc`` has already been called. ''' return self._safe_to_fork # Public methods ---------------------------------------------------------- [docs] def modify_document(self, doc): ''' Execute the configured ``func`` to modify the document. After this method is first executed, ``safe_to_fork`` will return ``False``. ''' try: self._func(doc) except Exception as e: if self._trap_exceptions: handle_exception(self, e) else: raise finally: self._safe_to_fork = False #----------------------------------------------------------------------------- # Private API #----------------------------------------------------------------------------- #----------------------------------------------------------------------------- # Code #-----------------------------------------------------------------------------