Source code for bokeh.driving

#-----------------------------------------------------------------------------
# Copyright (c) 2012 - 2021, Anaconda, Inc., and Bokeh Contributors.
# All rights reserved.
#
# 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 ...

'''

#-----------------------------------------------------------------------------
# Boilerplate
#-----------------------------------------------------------------------------
from __future__ import annotations

import logging # isort:skip
log = logging.getLogger(__name__)

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# Standard library imports
from functools import partial
from typing import (
    Any,
    Callable,
    Iterable,
    Iterator,
    Sequence,
    TypeVar,
)

#-----------------------------------------------------------------------------
# Globals and constants
#-----------------------------------------------------------------------------

__all__ = (
    'bounce',
    'cosine',
    'count',
    'force',
    'linear',
    'repeat',
    'sine',
)
#-----------------------------------------------------------------------------
# General API
#-----------------------------------------------------------------------------

[docs]def bounce(sequence: Sequence[int]) -> partial[Callable[[], None]]: ''' 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: int) -> int: 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: float, A: float = 1, phi: float = 0, offset: float = 0) -> partial[Callable[[], None]]: ''' 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: float) -> float: return A * cos(w*i + phi) + offset return partial(force, sequence=_advance(f))
[docs]def count() -> partial[Callable[[], None]]: ''' Return a driver function that can advance a simple count. ''' return partial(force, sequence=_advance(lambda x: x))
[docs]def force(f: Callable[[Any], None], sequence: Iterator[Any]) -> Callable[[], None]: ''' 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() -> None: f(next(sequence)) return wrapper
[docs]def linear(m: float = 1, b: float = 0) -> partial[Callable[[], None]]: ''' 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: float) -> float: return m * i + b return partial(force, sequence=_advance(f))
[docs]def repeat(sequence: Sequence[int]) -> partial[Callable[[], None]]: ''' 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: int) -> int: return sequence[i%N] return partial(force, sequence=_advance(f))
[docs]def sine(w: float, A: float = 1, phi: float = 0, offset: float = 0) -> partial[Callable[[], None]]: ''' 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: float) -> float: return A * sin(w*i + phi) + offset return partial(force, sequence=_advance(f))
#----------------------------------------------------------------------------- # Dev API #----------------------------------------------------------------------------- #----------------------------------------------------------------------------- # Private API #----------------------------------------------------------------------------- T = TypeVar("T") def _advance(f: Callable[[int], T]) -> Iterable[T]: ''' 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 #----------------------------------------------------------------------------- # Code #-----------------------------------------------------------------------------