#!/usr/bin/env python
# -*- encoding: utf-8 -*-
'''Presets provides an object interface to a module which can override
the default parameter values.
This is primarily useful for packages which contain many functions with overlapping
parameter sets. Presets can be used to consistently override all defaults at once,
while maintaining the same externally-facing API.
Example
-------
This example shows how to override common default parameters in the librosa package.
>>> import librosa as _librosa
>>> from presets import Preset
>>> librosa = Preset(_librosa)
>>> librosa['sr'] = 44100
>>> librosa['n_fft'] = 4096
>>> librosa['hop_length'] = 1024
>>> y, sr = librosa.load(librosa.util.example_audio_file())
>>> stft = librosa.stft(y)
>>> tempo, beats = librosa.beat.beat_track(y)
'''
import inspect
import os
import six
import types
import functools
from .version import version as __version__
[docs]class Preset(object):
'''The Preset class overrides the default parameters of functions within a module.
If the given module contains submodules, these are also encapsulated by Preset objects
that share the same default parameter dictionary.
Submodules are detected by examining common prefixes of the module source paths.
Attributes
----------
module : Python module
The module to encapsulate
dispatch : None or dictionary
A dictionary mapping modules to existing Preset objects.
This should be left as `None` for most situations.
defaults : None or dictionary
An existing dictionary object used to collect default parameters.
Note: this will be passed by reference.
'''
def __wrap(self, func):
'''This decorator overrides the default arguments of a function.
For each keyword argument in the function, the decorator first checks
if the argument has been overridden by the caller, and uses that value instead if so.
If not, the decorator consults the Preset object for an override value.
If both of the above cases fail, the decorator reverts to the function's native
default parameter value.
'''
def deffunc(*args, **kwargs):
'''The decorated function'''
# Get the list of function arguments
if hasattr(inspect, 'signature'):
# Python 3.5
function_args = inspect.signature(func).parameters
else:
function_args = inspect.getargspec(func).args
# Construct a dict of those kwargs which appear in the function
filtered_kwargs = kwargs.copy()
# look at all relevant keyword arguments for this function
for param in function_args:
if param in kwargs:
# Did the user override the default?
filtered_kwargs[param] = kwargs[param]
elif param in self._defaults:
# Do we have a clobbering value in the default dict?
filtered_kwargs[param] = self._defaults[param]
# Call the function with the supplied args and the filtered kwarg dict
return func(*args, **filtered_kwargs) # pylint: disable=W0142
wrapped = functools.update_wrapper(deffunc, func)
# force-mangle the docstring here
wrapped.__doc__ = ('WARNING: this function has been modified by the Presets '
'package.\nDefault parameter values described in the '
'documentation below may be inaccurate.\n\n{}'.format(wrapped.__doc__))
return wrapped
def __init__(self, module, dispatch=None, defaults=None):
# This defaults directory will get passed around by reference
if defaults is None:
defaults = dict()
self._defaults = defaults
self._module = module
if dispatch is None:
dispatch = dict()
dispatch[module] = self
self._dispatch = dispatch
modpath = os.path.dirname(inspect.getfile(module))
# inspect the target module
for attr, value in inspect.getmembers(module):
# If it's a function, wrap it
if six.callable(value):
# Wrap the function in a decorator
wrapped = self.__wrap(value)
setattr(self, attr, wrapped)
# If it's a module, construct a parameterizer to wrap it
elif (isinstance(value, types.ModuleType) and
hasattr(value, '__file__')):
# test if this is a submodule of the current module
submodpath = inspect.getfile(value)
if os.path.commonprefix([modpath, submodpath]) == modpath:
if value not in self._dispatch:
# We need to pre-seed the dispatch entry to avoid
# cyclic references
self._dispatch[value] = None
self._dispatch[value] = Preset(value,
dispatch=self._dispatch,
defaults=self._defaults)
setattr(self, attr, self._dispatch[value])
else:
setattr(self, attr, value)
def __getitem__(self, param):
return self._defaults[param]
def __delitem__(self, param):
del self._defaults[param]
def __contains__(self, param):
return param in self._defaults
def __setitem__(self, param, value):
self._defaults[param] = value
[docs] def keys(self):
'''Returns a list of currently set parameter defaults'''
return self._defaults.keys()
[docs] def update(self, D):
'''Updates the default parameter set by a dictionary D'''
self._defaults.update(D)