#-----------------------------------------------------------------------------
# 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 a set of decorators useful for repeatedly updating a
a function parameter in a specified way each time the function is
called.
These decorators can be especially useful in conjunction with periodic
callbacks in a Bokeh server application.
Example:
As an example, consider the ``bounce`` forcing function, which
advances a sequence forwards and backwards:
.. code-block:: python
from bokeh.driving import bounce
@bounce([0, 1, 2])
def update(i):
print(i)
If this function is repeatedly called, it will print the following
sequence on standard out:
.. code-block:: none
0 1 2 2 1 0 0 1 2 2 1 ...
'''
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# Boilerplate
#-----------------------------------------------------------------------------
from __future__ import absolute_import, division, print_function, unicode_literals
import logging
log = logging.getLogger(__name__)
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# Imports
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# Standard library imports
from functools import partial
# External imports
# Bokeh imports
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# Globals and constants
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__all__ = (
'bounce',
'cosine',
'count',
'force',
'linear',
'repeat',
'sine',
)
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# General API
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[docs]def bounce(sequence):
''' Return a driver function that can advance a "bounced" sequence
of values.
.. code-block:: none
seq = [0, 1, 2, 3]
# bounce(seq) => [0, 1, 2, 3, 3, 2, 1, 0, 0, 1, 2, ...]
Args:
sequence (seq) : a sequence of values for the driver to bounce
'''
N = len(sequence)
def f(i):
div, mod = divmod(i, N)
if div % 2 == 0:
return sequence[mod]
else:
return sequence[N-mod-1]
return partial(force, sequence=_advance(f))
[docs]def cosine(w, A=1, phi=0, offset=0):
''' Return a driver function that can advance a sequence of cosine values.
.. code-block:: none
value = A * cos(w*i + phi) + offset
Args:
w (float) : a frequency for the cosine driver
A (float) : an amplitude for the cosine driver
phi (float) : a phase offset to start the cosine driver with
offset (float) : a global offset to add to the driver values
'''
from math import cos
def f(i):
return A * cos(w*i + phi) + offset
return partial(force, sequence=_advance(f))
[docs]def count():
''' Return a driver function that can advance a simple count.
'''
return partial(force, sequence=_advance(lambda x: x))
[docs]def force(f, sequence):
''' Return a decorator that can "force" a function with an arbitrary
supplied generator
Args:
sequence (iterable) :
generator to drive f with
Returns:
decorator
'''
def wrapper():
f(next(sequence))
return wrapper
[docs]def linear(m=1, b=0):
''' Return a driver function that can advance a sequence of linear values.
.. code-block:: none
value = m * i + b
Args:
m (float) : a slope for the linear driver
x (float) : an offset for the linear driver
'''
def f(i):
return m * i + b
return partial(force, sequence=_advance(f))
[docs]def repeat(sequence):
''' Return a driver function that can advance a repeated of values.
.. code-block:: none
seq = [0, 1, 2, 3]
# repeat(seq) => [0, 1, 2, 3, 0, 1, 2, 3, 0, 1, ...]
Args:
sequence (seq) : a sequence of values for the driver to bounce
'''
N = len(sequence)
def f(i):
return sequence[i%N]
return partial(force, sequence=_advance(f))
[docs]def sine(w, A=1, phi=0, offset=0):
''' Return a driver function that can advance a sequence of sine values.
.. code-block:: none
value = A * sin(w*i + phi) + offset
Args:
w (float) : a frequency for the sine driver
A (float) : an amplitude for the sine driver
phi (float) : a phase offset to start the sine driver with
offset (float) : a global offset to add to the driver values
'''
from math import sin
def f(i):
return A * sin(w*i + phi) + offset
return partial(force, sequence=_advance(f))
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# Dev API
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#-----------------------------------------------------------------------------
# Private API
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def _advance(f):
''' Yield a sequence generated by calling a given function with
successively incremented integer values.
Args:
f (callable) :
The function to advance
Yields:
f(i) where i increases each call
'''
i = 0
while True:
yield f(i)
i += 1
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# Code
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