Source code for bokeh.core.property.override
#-----------------------------------------------------------------------------
# Copyright (c) 2012 - 2018, Anaconda, Inc. All rights reserved.
#
# Powered by the Bokeh Development Team.
#
# The full license is in the file LICENSE.txt, distributed with this software.
#-----------------------------------------------------------------------------
''' Provide the ``Override`` class, for overriding base class property
attributes.
.. note::
This class should normally be imported from ``bokeh.core.properties``
instead of directly from this module.
'''
#-----------------------------------------------------------------------------
# Boilerplate
#-----------------------------------------------------------------------------
from __future__ import absolute_import, division, print_function, unicode_literals
import logging
log = logging.getLogger(__name__)
#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
# Standard library imports
# External imports
# Bokeh imports
#-----------------------------------------------------------------------------
# Globals and constants
#-----------------------------------------------------------------------------
__all__ = (
'Override',
)
#-----------------------------------------------------------------------------
# General API
#-----------------------------------------------------------------------------
[docs]class Override(object):
''' Override attributes of Bokeh property in derived Models.
When subclassing a Bokeh Model, it may be desirable to change some of the
attributes of the property itself, from those on the base class. This is
accomplished using the ``Override`` class.
Currently, ``Override`` can only be use to override the ``default`` value
for the property.
Keyword Args:
default (obj) : a default value for this property on a subclass
Example:
Consider the following class definitions:
.. code-block:: python
from bokeh.model import Model
from bokeh.properties import Int, Override
class Parent(Model):
foo = Int(default=10)
class Child(Parent):
foo = Override(default=20)
The parent class has an integer property ``foo`` with default value
10. The child class uses the following code:
.. code-block:: python
foo = Override(default=20)
to specify that the default value for the ``foo`` property should be
20 on instances of the child class:
.. code-block:: python
>>> p = Parent()
>>> p.foo
10
>>> c = Child()
>>> c.foo
20
'''
def __init__(self, **kwargs):
if len(kwargs) == 0:
raise ValueError("Override() doesn't override anything, needs keyword args")
self.default_overridden = 'default' in kwargs
if self.default_overridden:
self.default = kwargs.pop('default')
if len(kwargs) > 0:
raise ValueError("Unknown keyword args to Override: %r" % (kwargs))
#-----------------------------------------------------------------------------
# Dev API
#-----------------------------------------------------------------------------
#-----------------------------------------------------------------------------
# Private API
#-----------------------------------------------------------------------------
#-----------------------------------------------------------------------------
# Code
#-----------------------------------------------------------------------------